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  • Articles  (196,191)
  • Polymer and Materials Science  (112,478)
  • Inorganic Chemistry  (83,670)
  • 42.74
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  • 1
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-02-10
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-01-27
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-01-27
    Description: Polynitrogens have the potential for ultrahigh-performing explosives or propellants because singly or doubly bonded polynitrogens can decompose to triply bonded dinitrogen (N2) with an extraordinarily large energy release. The large energy content and relatively low activation energy toward decomposition makes the synthesis of a stable polynitrogen allotrope an extraordinary challenge. Many elements exist in different forms (allotropes)—for example, carbon can exist as graphite, diamond, buckyballs, or graphene. However, no stable neutral allotropes are known for nitrogen, and only two stable homonuclear polynitrogen ions had been isolated until now—namely, the N3− anion (1) and the N5+ cation (2). On page 374 of this issue, Zhang et al. (3) report the synthesis and characterization of the first stable salt of the cyclo-N5− anion, only the third stable homonuclear polynitrogen ion ever isolated. Author: Karl O. Christe
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-09-09
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-11-11
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2015-11-07
    Description: The earliest known crabs are of Early and Middle Jurassic age; in general, they are rare. Here we describe a new species of homolodromioid from the late Bathonian of Sarthe (France), based on a single dorsal carapace, Tanidromites raboeufi n. sp. This specimen has mostly well-preserved cuticle, and shows two episkeletozoans (bryozoan colonies) on its dorsal side, which is unique amongst early brachyurans (Early and Middle Jurassic). These bryozoans are identified as juvenile colonies of the morphogenus Berenicea (sheet-like tubuluporines), typical encrusters of hard substrates. Their presence directly on the carapace crab shows that they were closely cohabitating with this early brachyuran in its palaeoenvironment. One of these colonies appears to have attached to the internal carapace surface, indicative of post-mortem settlement and growth. Colony sizes suggest a growth phase of at least several months on the sea floor, implying a certain resistance to decomposition of the crab carapace. This is of note in the light of extant homolodromioids which are known to have extremely fragile carapaces. This association demonstrates that post-mortem associations may yield palaeoecological insights into both substrate and colonising organisms.
    Keywords: Bathonian ; cyclostome bryozoans ; epibiosis ; episkeletozoans ; Homolodromioidea ; 38.22 ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
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  • 7
    Publication Date: 2016-05-06
    Description: All squat lobsters of the families Galatheidae, Munididae and Munidopsidae from the Miocene of the Central Paratethys are reviewed taxonomically. Based on additional observations emended diagnoses are provided for Agononida cerovensis and Galathea weinfurteri, from the Lower and Middle Miocene, respectively. Munidopsis is represented by two species in the study area; additional data for M. lieskovensis from the Lower Miocene of Slovakia are presented and a new species, M. palmuelleri, from the Middle Miocene of Slovenia is erected. Implications for palaeoenvironmental reconstructions are briefly discussed for each taxon.
    Keywords: Neogene ; Austria ; Slovakia ; revision ; new species ; 42.74 ; 38.22
    Repository Name: National Museum of Natural History, Netherlands
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  • 8
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    In:  Various articles (0007-4977) vol.91 (2015) nr.2 p.205
    Publication Date: 2016-08-18
    Keywords: gall crab ; Opecarcinus hypostegus ; Curaçaoan reef ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
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  • 9
    Publication Date: 2016-08-18
    Description: A new species of gall crab is described from the free-living stony coral Trachyphyllia geoffroyi. Specimens were collected during field work in Lembeh Strait (Indonesia) and of Kudat (Malaysian Borneo). This new species, here named Lithoscaptus semperi sp. n., is the ninth species assigned to the genus. It can be separated from its congeners by not having the internal orbital angle extending beyond the external orbital angle, and by the stout female P2 merus with prominent distomesial projection. In addition, the carapace surface appears smooth, despite having small tubercles on the anterior half, and is without noticeable spines, other than those on the frontal margin. The distinctive carapace pattern in life is a diagnostic character in male specimens.
    Keywords: Cospeciation ; host specificity ; Indonesia ; Malaysia ; Thoracotremata ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 10
    Publication Date: 2015-12-07
    Description: The emergence of king crabs from a hermit crab-like ancestor is one of the most curious events in decapod evolution. King crabs comprise two taxa, Lithodidae and Hapalogastridae, and while lithodids have formed the focus of various anatomical studies, the internal anatomy of hapalogastrids has never been studied although this group might represent a more ancestral morphological condition within king crabs than lithodids do. To better understand the evolutionary transformation of pagurid-like hermit crabs into king crabs, we studied the hemolymph vascular system and associated organs of representatives of Hapalogaster and present here the first micro-computer tomography data pertaining to the internal anatomy of hapalogastrids. Our results for Hapalogastridae are compared with existing and new data on Paguridae and Lithodidae and are discussed in the light of the process of carcinization or evolutionary transformation into a crab-like habitus. Hapalogaster resembles both pagurids on the one hand and lithodids on the other, not only with regard to external morphological characters but also in terms of certain internal anatomical features. In this and other respects, Hapalogaster represents an evolutionary intermediate form that connects pagurids and lithodids.
    Keywords: Anomala ; carcinization ; circulatory system ; evolutionary morphology ; structural coherence ; variability ; 42.74 ; 38.22 ; 42.62
    Repository Name: National Museum of Natural History, Netherlands
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  • 11
    Publication Date: 2015-10-27
    Description: The centipedes of the clade Epimorpha change slightly during post-embryonic growth but there is huge variation between species in the maximum body size. New specimens of the rarely collected Neotropical genus Dinogeophilus provide further evidence that this genus comprises the smallest species of the Epimorpha, with a recorded maximum length of 5.5 mm. Up to now Dinogeophilus has been invariantly classified in Geophilidae but different sources of evidence (examination by SEM, cladistic evaluation of morphology, similarity and phylogenetic analysis of molecular data) agree on a very different phylogenetic hypothesis: Dinogeophilus is actually a derived lineage of Schendylidae, only distantly related to Geophilidae, and possibly belong to a mainly Neotropical subgroup of schendylids. A comparison of Dinogeophilus with the most closely related taxa suggests that body miniaturization was accompanied by possibly paedomorphic traits, including lower number of some multiple elements (antennal sensilla, processes on the mouth-parts, coxal organs) and shorter setae. Possibly associated with miniaturization are also a few novel features of Dinogeophilus, among which the unique subterminal denticles of the forcipules, suggesting a possible change in the feeding behaviour.
    Keywords: Geophilidae ; miniaturization ; molecular phylogeny ; paedomorphosis ; Schendylidae ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 12
    Publication Date: 2016-08-18
    Description: A new species of cryptochirid crab, Fizesereneia panda van der Meij, is described and illustrated based on specimens collected from the scleractinian corals Lobophyllia cf. hemprichii and L. cf. corymbosa from the Farasan Banks, Farasan Islands, and the reefs off Thuwal in the Saudi Arabian Red Sea, and from Symphyllia recta from reefs in the Gulf of Oman. This is the second cryptochirid species with the Red Sea as type locality. It can be separated from its congeners by the subrectangular carapace, raised midline and the complete division of the carapace depressions, and reddish black colour pattern of these concavities in live specimens. This new species is the seventh assigned to Fizesereneia. A DNA barcode for the new species has been deposited in GenBank.
    Keywords: DNA barcoding ; gall crabs ; host specificity ; Lobophylliidae ; Saudi Arabia ; Scleractinia ; taxonomy ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 13
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    In:  Various articles (1445-5226) vol.28 (2014) p.491
    Publication Date: 2016-08-18
    Description: The enigmatic gall crab family Cryptochiridae has been proposed to be phylogenetically derived from within the Grapsidae (subsection Thoracotremata), based on the analysis of 16S mtDNA of one cryptochirid, Hapalocarcinus marsupialis, among a wide array of thoracotremes, including 12 species of the family Grapsidae. Here,wetest the monophyly and phylogenetic position of Cryptochiridae using the same gene, but with an extended representation of cryptochirids spanning nine species in eight of 21 genera, in addition to further thoracotreme representatives. The results show that gall crabs form a highly supported monophyletic clade within the Thoracotremata, which evolved independently of grapsid crabs. Therefore, the Cryptochiridae should not be considered as highly modified Grapsidae, but as an independent lineage of Thoracotremata, deserving its current family rank. Further molecular and morphological studies are needed to elucidate the precise placement of the cryptochirids within the Eubrachyura.
    Keywords: 16S mtDNA ; coral-associated organisms ; evolutionary origin ; superfamily ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 14
    Publication Date: 2016-08-18
    Description: Coral-associated invertebrates dominate the biodiversity of coral reefs. Some of the associations involving symbiotic invertebrates remain unknown or little studied. This holds true even for relatively wellstudied coral reefs, like those in the Caribbean Sea. Coral gall crabs (Cryptochiridae), obligate symbionts of stony corals, form a much-overlooked component of coral reef communities. Most recent studies on the Atlantic members of Cryptochiridae have been conducted off Brazil and little recent data have become available from the Caribbean region. During fieldwork off Curaçao (southern Caribbean Sea), eight new host coral species, belonging to four coral families, were recorded for three cryptochirid species. Kroppcarcinus siderastreicola Badaro, Neves, Castro and Johnsson, 2012, previously only known from Brazil, and Opecarcinus hypostegus (Shaw and Hopkins, 1977) are new additions to the fauna of Curaçao. Besides the new hosts and geographic range extensions, a free-living male Troglocarcinus corallicola Verrill, 1908 was observed visiting a female of the same species lodged in her gall in an Orbicella annularis (Ellis and Solander, 1786) colony. This is the first photodocumented record of the “visiting” mating system in Cryptochiridae.
    Keywords: shallow-water gall crabs ; Decapoda ; Cryptochiridae ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 15
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    In:  Contributions to Zoology (13834517) vol.75, 1/2 (2006) p.1
    Publication Date: 2014-11-07
    Description: We have examined the caudal regions of diverse peracarid and pancarid malacostracans using light and scanning electronic microscopy. The traditional view of malacostracan posterior anatomy is not sustainable, viz., that the free telson, when present, bears the anus near the base. The anus either can occupy a terminal, sub-terminal, or mid-ventral position on the telson; or can be located on the sixth pleomere – even when a free telson is present. Furthermore, there is information that might be interpreted to suggest that in some cases a telson can be absent. Embryologic data indicates that the condition of the body terminus in amphipods cannot be easily characterized, though there does appear to be at least a transient seventh segment that seems to fuse with the sixth segment. Our understanding of the genesis of the so-called telson of amphipods could be subject to alternative interpretations than those traditionally put forth.
    Keywords: anus ; Pancarida ; Peracarida ; pleomeres ; proctodaeum ; teloblasts ; telson ; urosome ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 16
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    In:  Contributions to Zoology (13834517) vol.75, 3/4 (2006) p.189
    Publication Date: 2014-11-07
    Description: Small populations of several species of the groundwater dwelling amphipod genus Ingolfiella are found in caves, wells, seabottoms, beaches and riverbed interstitial habitats. To gain insight in the socio-ecology of these elusive species, we used data from collected specimens to explore the relationships between sexratios, display of secondary sexual characters and other morphological features, and habitat use. We extracted data on the sex ratios and the presence-absence of secondary sexual characters of 13 species from the literature and through examination of museum material. We found a clearly skewed sex ratio with a preponderance of females, both in the individual species as in the genus as a whole. However, sex ratio and the display of secondary sexual characters were not correlated, nor did these characters correlate with the amount of sexual dimorphism. It remains unknown why so many ingolfiellids have evolved these costly features.
    Keywords: arthropod sex ratio ; socio-ecology ; groundwater amphipods ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 17
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    In:  Contributions to Zoology (13834517) vol.75, 3/4 (2006) p.169
    Publication Date: 2014-11-07
    Description: The amphipod family Stenothoidae contains more than 200 species in about 40 genera; these genera are at present often defined not by the presence, but by the absence of synapomorphies, thus defining grades rather than clades. Our phylogenetic analyses yielded 4 groups of stenothoids: a basic proboloidid clade; an advanced and always clearly separated Austral-Antarctic thaumatelsonid clade, with a possibly related Arctic mesometopid clade; and finally a poorly resolved group, the stenothoids sensu stricto, including the large and probably polyphyletic genera Stenothoe and Metopa, each with more than 50 species. It is proposed to study and analyse these groups separately in future, based on better redescriptions of the individual species. Our analyses support the family status of the Thaumatelsonidae, erected as a family by Gurjanova in 1938, but reduced to subfamily rank by Barnard in 1972.
    Keywords: Taxonomy ; Amphipoda ; Stenothoidae ; Thaumatelsonidae ; phylogenetic analysis ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 18
    Publication Date: 2014-11-07
    Description: Two new brachyuran species are described for the Upper Cretaceous Mexcala Formation, Guerrero State, Mexico. Longusorbis quadratus new species (Coniacian, Temalac region) is the oldest and southernmost record for the genus. Xanthosia zoquiapensis new species (Campanian, Zoquiapa region) is the first record for the genus in Mexico. In addition, the age for Costacopluma bishopi Vega and Feldmann is discussed (Coniacian, Temalac region) and represents the oldest and southernmost record for Cretaceous representatives of this genus in North America. All specimens are considerably smaller compared to other species of the same genera and are interpreted as the first example of brachyuran dwarfism in the geological record. These species add new insight into possible migratory routes during the Late Cretaceous. Within Longusorbis, a northwestern migratory route is documented from the Coniacian in Mexico to the Campanian - Maastrichtian of the west coast of North America (Canada), whereas within the genus Xanthosia, a western migratory route from the Albian of Europe to the Campanian of Mexico is indicated. Costacopluma migrated east and north to the west coast of Africa, southeast North America and Greenland.
    Keywords: Dwarfism ; decapoda ; Cretaceous ; new species ; Mexico ; 38.22 ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 19
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    In:  Zoologische Mededelingen (0024-0672) vol.80 (2006) nr.4 p.33
    Publication Date: 2010-12-12
    Description: A new species of sponge-associated pontoniine shrimp from Zanzibar is described and illustrated and its systematic position is discussed.
    Keywords: Crustacea ; Decapoda ; Pontoniinae ; Periclimenaeus fawatu spec. nov. ; sponge associate ; Zanzibar ; Indian Ocean ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 20
    Publication Date: 2014-11-07
    Description: A phylogenetic analysis was conducted including representatives from all recognized extant and extinct families of the Xanthoidea sensu lato, resulting in one new family, Hypothalassiidae. Four xanthoid families are elevated to superfamily status, resulting in Carpilioidea, Pilumnoidoidea, Eriphioidea, Progeryonoidea, and Goneplacoidea, and numerous subfamilies are elevated to family status. The Mathildellidae is moved from the Goneplacidae to the Portunoidea. Diagnoses for all superfamilies and families discussed herein are provided, embracing characters typically used by biologists as well as readily fossilized features of the dorsal carapace, sternum, abdomen, and chelipeds. All genera known from the fossil record at one time referred to the Xanthidae sensu lato, Xanthoidea sensu lato, or Goneplacidae sensu lato were evaluated as to their family level placement and as a result, the family-level placement of many of these genera has been changed herein. Balcacarcinus new substitute name, is provided herein for Bittneria Schweitzer and Karasawa, 2004.
    Keywords: Crustacea ; Decapoda ; Brachyura ; Xanthoidea ; Portunidae ; systematics ; phylogeny ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 21
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    In:  Zoologische Mededelingen (00240672) vol.80 (2006) nr.4 p.9
    Publication Date: 2010-12-12
    Description: The debate on a proper subdivision of the large genus Uca was initiated by the conflicting proposals of Bott (1973) and Crane (1975). In spite of recent computer-aided mending attempts, the overall situation (instability of Uca systematics and nomenclature) has not convincingly improved. Here we try to settle the debate by presenting a simple cladistic analysis sensu Hennig (1950) based on selected morphological characters supplemented by functional remarks and a few behavioural data resulting from fieldwork. All 94 species (except six) were examined, mostly by using the authors’ collection of Uca (partly in Marburg and partly deposited in the Leiden Museum) and all species (see list in chapter 5) are assigned to one of the eight subgenera recognized: Australuca, Cranuca subgen. nov., Gelasimus, Leptuca, Minuca, Paraleptuca, Tubuca, Uca s. str. Some emphasis is laid on a differentiation within the synapomorphies selected: five “major unique inventions” (table 1) are delimited from normal apomorphic character states. The discussion is confined to zoogeographical conclusions, which refer to an early dispersal within “Wegener’s Indo-Atlantic Ocean” and which favour Australia as the centre of origin of the genus Uca.
    Keywords: fiddler crabs ; subgenera ; cladistic analysis ; morphology ; “major unique inventions” ; zoogeography ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 22
    Publication Date: 2010-12-12
    Description: A new species of crayfish, Cherax (Cherax) holthuisi spec. nov., is described and illustrated on the basis of nine specimens collected from Aitinjo Lake, Irian Jaya, Indonesia.
    Keywords: Crustacea ; Decapoda, Parastacidae ; Cherax (Cherax) holthuisi ; new species ; freshwater crayfish, Irian Jaya ; Indonesia ; West New Guinea ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 23
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    In:  Zoologische Mededelingen (0024-0672) vol.80 (2006) nr.4 p.71
    Publication Date: 2010-12-12
    Description: A new genus, Soceulia, is established for Leucosia species with third to fifth segments of the male abdomen fused, the first male pleopod with shaft coiled once on its axis, and terminating in a digitate apical process encased in a setose muff: L. marmorea Bell, 1855, L. brunnea Miers, 1877, L. major Chen & Ng, 2003, and a new species, S. alainia. The species are described or redescribed and illustrated, extended synonymies are given, and a key for their identification is provided.
    Keywords: Decapoda ; Leucosiidae ; Leucosia ; Soceulia ; new genus ; new species ; Indo-Pacific ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 24
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    In:  Zoologische Mededelingen (0024-0672) vol.80 (2006) nr.4 p.55
    Publication Date: 2010-12-12
    Description: A new genus, Coleusia, is established for Leucosia species with segments 3-5 of the male abdomen fused, the shaft of the male’s first pleopod coiled thrice on its axis, bearing distally a setose lobe and an elongate apical process: L. biannulata Tyndale-Biscoe & George, 1962, L. magna Tyndale-Biscoe & George, 1962, L. signata Paulson, 1875, and L. urania (Herbst, 1801), and a new species: C. rangita. The species are described or redescribed and illustrated, extended synonymies are given, and a key for their identification is provided.
    Keywords: Decapoda ; Leucosiidae ; Leucosia ; Coleusia ; new genus ; new species ; Indo-Pacific ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 25
    Publication Date: 2010-12-12
    Description: During the DIVA-2 cruise (May 31 - July 4, 1994, see Desbruyères et al., 1994) and the PICO cruise (June 25 – July 11, 1998, N/O Nadir, PI: D. Desbruyères) to the Azores Triple Junction Area, two rare species of caridean shrimp were collected. Seven specimens of the pandalid Plesionika alexandri (A. Milne Edwards, 1883) were collected at the Lucky Strike hydrothermal vent field (37°20’N), and one specimen of the pontoniine Periclimenes kornii (Lo Bianco, 1903), at the Menez Gwen hydrothermal vent field (37°50’N). These hydrothermal vent fields are located on the Mid-Atlantic Ridge SW of the Azores. Both species of shrimp are only known from a few specimens. The original description of Plesionika alexandri was based on an incomplete specimen. It is now re-described on the bases of the present material
    Keywords: Crustacea ; Decapoda ; Caridea ; Plesionika alexandri, re-description, Periclimenes kornii ; Mid-Atlantic Ridge ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 26
    Publication Date: 2007-01-16
    Description: Two new species of sesarmid crabs are described from the mangroves of Timika in Papua (= Irian Jaya), Indonesia. Haberma kamora spec. nov. is the second species in the genus described from Singapore, differing from the type species in the form of its male first pleopods and possessing relatively more slender ambulatory legs. Parasesarma charis spec. nov. resembles P. erythrodactyla, P. tripectinis and to some extent, P. lepidum, but has different ambulatory leg proportions and a distinctive male first pleopod structure. Parasesarma acis Davie, 1993, is regarded as a junior synonym of P. tripectinis Shen, 1940.
    Keywords: Crustacea ; Decapoda ; Brachyura ; Sesarmidae ; taxonomy ; Haberma ; Parasesarma ; new species ; Indonesia ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 27
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    In:  Zoologische Mededelingen (00240672) vol.79-2 (2005) p.9
    Publication Date: 2007-01-16
    Description: A new genus, Urnalana, is established for Leucosia species with an urn-shaped carapace: L. angulata Rathbun, 1911, L. chevretii Haswell, 1880, L. cumingii Bell, 1855, L. elata A. Milne Edwards, 1874, L. elatoides Bouvier, 1915, L. hilaris Nobili, 1905, L. haematostica Adams & White, 1849, L. insularis Takeda & Kurata, 1976, L. margaritata A. Milne Edwards, 1874, L. pulchella Bell, 1855, L. purarensis Ovaere, 1987, L. thysanotus George & Clark, 1976, L. whitei Bell, 1855, and three new species: U. elatula, U. granulimera, and U. parahaematostica. The species are described or redescribed and illustrated, extended synonymies are given, and a key for their identification is provided.
    Keywords: Decapoda ; Leucosiidae ; Leucosia ; new genus ; new species ; Indo-Pacific ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 28
    Publication Date: 2014-11-07
    Description: A small collection of copepod samples from several wells in the Canterbury region, South Island, was examined. It contained a few cosmopolitan cyclopoid species, three interesting harpacticoids, as well as two new cyclopoid genera. The latter are presented in this paper, together with a redescription and first description of the male of Goniocyclops silvestris Harding, 1958, a cyclopoid species previously known only from North Island. Both new genera are from the Diacyclops-Acanthocyclops complex. Abdiacyclops gen. nov. is easily distinguishable from the complex by its unique swimming legs segmentation formula (2/2, 3/3, 3/3, 3/3), and is so far monospecific and known only after females. The most important characters of the second new genus, Zealandcyclops gen. nov. are: the swimming legs segmentation formula of 2/2, 3/2, 3/2, 3/2; a very small and two-segmented fifth leg; 11-segmented antennula; and sexual dimorphism in the swimming legs, with a transformed apical spine on the third leg endopod in the male. Four species were included in this genus: Zealandcyclops fenwicki sp. nov., from a well in the South Canterbury region; Z. haywardi sp. nov., from a well in the North Canterbury region; Z. eulitoralis (Alekseev and Arov, 1986) comb. nov., from the interstitial of several beaches on the southern shore of Lake Baikal; and Z. biceri (Boxshall et al., 1993) comb. nov., from a sandy beach on the western shore of Lake Baikal. Zealandcyclops gen. nov. seems to be an archaic cyclopoid genus, having survived only in New Zealand and in the ancient Lake Baikal. With the present report, the New Zealand cyclopoid fauna numbers 16 species, a systematic list of which is presented in this paper. The majority of them are cosmopolitan elements, probably introduced here by early European settlers. Only one genus (8%) and six species (38%) are endemic, which is probably a reflection of the absence of any comprehensive research on the New Zealand cyclopoids.
    Keywords: Stygofauna ; Cyclopoida ; New Zealand ; taxonomy ; Abdiacyclops ; Zealandcyclops ; Goniocyclops ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 29
    Publication Date: 2014-11-07
    Description: Strandesia kimberleyi n. sp. is described from subterranean waters of the Kimberley Region (Western Australia). It belongs to the group of relatively elongated Strandesia Stuhlmann, 1888 species, with no projection on the carapace and with a finely serrated posterior margin of the CR and its claws. The new species is characterized by the asymmetrical valves, elongated terminal segment of the maxillular palp, and the presence of a sensory organ antero-proximally on the first segment of the antennula. This is the first time that this organ is reported in the genus Strandesia. Strandesia purpurascens (Brady, 1886) is redescribed, while for S. variegata (Sars, 1901) and S. obliqua (Brady, 1868) some additional notes on the morphology are provided. A key to identification of 67 species of Strandesia is here given. This number includes a new species and two new combinations (S. iheringi (Sars, 1901) comb. nov., and S. mollis (Furtos, 1936) comb. nov.). Strandesia ewaldi is proposed as a nomen novum for S. labiata Roessler, 1990, while 31 species are proposed to be synonyms.
    Keywords: taxonomy ; Ostracoda ; Cyprididae ; Strandesia ; key ; 42.74
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  • 30
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    In:  Contributions to Zoology (13834517) vol.74, 3/4 (2005) p.313
    Publication Date: 2014-11-07
    Keywords: Arthropods ; Crustacea ; review ; festschrift ; Fredrick R. Schramm ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
    Type: Book review
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  • 31
    Publication Date: 2014-11-07
    Description: A new species of amphipod, Bathyporeia watkini sp. nov. from the Atlantic coasts of North Africa is described. This very characteristic species is abundant in some lagoons and estuaries near 28°N. New morphological information on B. elkaimi d’Udekem d’Acoz and Menioui, 2004 is given after specimens that were recently collected on the Atlantic coasts of southern Spain and South Portugal. The male of B. ledoyeri d’Udekem d’Acoz and Menioui, 2004 is described for the first time and new records of North African B. guilliamsoniana (Bate, 1857) and B. chevreuxi d'Udekem d'Acoz and Vader, 2005a are discussed.
    Keywords: Bathyporeia ; Crustacea ; Amphipoda ; taxonomy ; North Africa ; Spain ; Portugal ; eastern Atlantic ; 42.74
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  • 32
    facet.materialart.
    Unknown
    In:  Scripta Geologica (03757587) vol.130 (2005) p.187
    Publication Date: 2007-01-15
    Description: For fossil verrucid barnacles, the name Verruca withersi appears to have been used twice; Schram & Newman described material from the Albian-Cenomanian (Cretaceous) of Colombia, while Kruizinga had previously recorded a new species from the Pleistocene(?) or perhaps younger strata of Sumba (Indonesia). We do not consider V. withersi Schram & Newman to be a cirripede, therefore no replacement name is needed for this junior synonym. Verruca withersi Kruizinga is a valid species related to the extant V. cookei.
    Keywords: Crustacea ; Cirripedia ; Thoracica ; Verrucidae ; homonymys ; 42.74
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  • 33
    Publication Date: 2007-01-16
    Description: The main aim of the present paper is to delimit ‘true’ Spermophora, i.e. the group of species most closely related to the type species S. senoculata (Dugès). Apart from the type species, only three previously described species are included in this core group (S. estebani Simon, S. paluma Huber, S. yao Huber), together with nine newly described species: S. kerinci, S. tumbang, S. dumoga, S. maros, S. deelemanae, S. palau, S. kaindi, S. luzonica, and S. sumbawa. Except for the Holarctic and anthropophilic type species, all species have limited distributions in Southeast Asia, northeastern Australia, and the Pacific Islands, where they inhabit the leaf litter layer of tropical forests as well as caves. A tight correlation is documented in Spermophora between the male cheliceral apophyses (distance between the tips) and the pockets on the female external genitalia. In addition, three new Southeast Asian genera are described that appear similar to Spermophora but do not share the synapomorphies of the genus: Aetana n. gen. with three new species from the Philippines (A. omayan), Borneo (A. kinabalu), and Fiji (A. fiji); Savarna n. gen., with one new species from southern Thailand (S. thaleban) and two species from Sumatra and Malaysia transferred from Spermophora [Savarna tessellata (Simon) n. comb., and S. baso (Roewer) n. comb.]; and Khorata n. gen., with four new species from Thailand (K. bangkok, K. schwendingeri) and Laos (K. khammouan, K. jaegeri).
    Keywords: Araneae ; Pholcidae ; Spermophora ; revision ; taxonomy ; Southeast Asia ; Pacific ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 34
    facet.materialart.
    Unknown
    In:  Zoologische Mededelingen (00240672) vol.79-2 (2005) p.41
    Publication Date: 2007-01-16
    Description: A new genus, Seulocia, is established for Leucosia species with segments 3-6 of the male abdomen fused, and the first male pleopod with straight shaft, twisted once on its axis: L. laevimana Miers, 1884, L. latirostrata Shen & Chen, 1978, L. pubescens Miers, 1877, L. pulchra Shen & Chen, 1978, L. rhomboidalis de Haan, 1841, L. truncata Alcock, 1896, and L. vittata Stimpson, 1858, and three new species: S. anahita, S. crepuscula, S. cristata. The species are described or redescribed and illustrated, extended synonymies are given, and a key for their identification is provided. The choice of the lectotype of L. rhomboidalis is discussed.
    Keywords: Decapoda ; Leucosiidae ; Leucosia ; Seulocia ; new genus ; new species ; Indo-Pacific ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 35
    Publication Date: 2014-11-07
    Description: We investigated mtDNA genetic differentiation and the phylogenetic relationships of 11 populations of the oniscidean genus Ligidium. We studied nine populations from Greece, assigned to three nominal species (L. euboicum, L. germanicum and L. beieri), and two from central Europe (L. germanicum and L. hypnorum), applying RFLP analysis of two mtDNA segments (12S rDNA and 16S rDNA) amplified by PCR. The analysis revealed seven monomorphic and four polymorphic populations, and 17 different haplotypes, each one present in one population only. Several restriction enzymes produced population specific patterns, enabling discrimination among the different populations. The estimated net nucleotide divergence between populations ranges from 1.06 to 16.52%, while the high NST value (0.96) indicates the existence of increased interpopulation genetic differentiation that can be attributed to the extreme isolation among Ligidium populations. The relationships between haplotypes and populations are not congruent with their geographical distribution and the established taxonomy within the genus.
    Keywords: Oniscidea ; Greece ; mtDNA ; RLFPs ; genetic isolation ; Ligidium ; isopods ; 16S rDNA ; 12S rDNA ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 36
    Publication Date: 2007-01-18
    Description: In recent sampling along the Colombian Caribbean coast, three species of the genus Plesionika (P. gigliolii, P. longicauda, and P. willesi) have been added to the seven reported upon by Campos et al. (in press). P. gigliolii is now recorded for the first time from the West Atlantic. The taxonomic status of P. acanthonotus is discussed. A key to the Atlantic species of Plesionika is provided.
    Keywords: Caridea ; Pandalidae ; Plesionika ; range extensions ; West Atlantic ; Colombia ; key ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 37
    Publication Date: 2007-01-18
    Description: New localities and records of pseudoscorpions are given for the Leeward Islands, the Windward Islands and Curaçao. The protonymph of Serianus gratus Hoff, 1964, from Curaçao is described.
    Keywords: Pseudoscorpiones ; Aphelolpium scitulum ; Aphelolpium brachytarsus ; Pachyolpium arubense arubense ; Serianus gratus ; Leeward Islands ; Windward Islands ; Curaçao ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 38
    facet.materialart.
    Unknown
    In:  Zoologische Mededelingen (00240672) vol.78, 1-16 (2004) p.275
    Publication Date: 2007-01-18
    Description: Cordylochernes scorpioides (Linnaeus, 1758) (Pseudoscorpiones: Chernetidae) is redescribed and illustrated.
    Keywords: Chernetidae ; Cordylochernes scorpioides ; Brazil ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 39
    Publication Date: 2007-01-09
    Description: Eoferreola rhombica, a pompilid new to the Dutch fauna, and its remarkable host, Eresus sandaliatus (Hymenoptera: Pompilidae; Araneae: Eresidae) In 1998 a female specimen of Eoferreola rhombica (Christ, 1791) was collected in a road-verge on the Veluwe. The nearest populations of this species are found in northern France and eastern Germany. It is possible that this insect was transported by traffic from one of these populations. However at the collection site a large population of the rare host spider Eresus sandaliatus (Martini & Goeze, 1778) is known to be present for many years. Therefore the presence of a population of E. rhombica cannot be excluded. Future observations have to reveal the status of this spider wasp in the Netherlands.
    Keywords: Hymenoptera ; Pompilidae ; Eoferreola rhombica ; Araneae ; Eresidae ; Eresus sandaliatus ; Biologie ; Verspreiding ; Herkenning ; Nederland ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 40
    facet.materialart.
    Unknown
    In:  Nederlandse Faunistische Mededelingen (01692453) vol.9 (1999) p.7
    Publication Date: 2007-01-09
    Description: The amphipod Echinogammarus stoerensis not extinct in The Netherlands (Crustacea: Amphipoda: Gammaridea) The gammaridean amphipod Echinogammarus stoerensis has never been a common species in the Netherlands, due to the scarcity of suitable habitats. It is typically found under boulders on a gravelly substrate, where a freshwater flow occurs over the littoral zone. As a result of reinforcement of sea dykes, the typical habitat disappeared from The Netherlands. However, E. stoerensis proves to survive in less suited substrates with more silt, and freshwater supply only from rain.
    Keywords: Crustacea ; Amphipoda ; Gammaridea ; Verspreiding ; Herkenning ; Nederland ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 41
    facet.materialart.
    Unknown
    In:  Nederlandse Faunistische Mededelingen (01692453) vol.9 (1999) p.103
    Publication Date: 2007-01-10
    Description: The millipede Archiboreoiulus pallidus, new to the Dutch fauna (Myriapoda: Diplopoda) Some specimens of the millipede Archiboreoiulus pallidus (Brade-Birks, 1920) were found in April 1996 in ‘het Bovenste Bos’, a deciduous forest south of Epen, in the province of Limburg. Two weeks later, a visit was paid to the collection of the Plant Protection Service and this resulted in a second record of this species. This specimen was found in June 1977 in an agricultural field near Maastricht, about 15 km west of Epen (province of Limburg). This is the first record of A. pallidus for the Dutch fauna. This species is morphologically very similar to Blaniulus guttulatus. The most important characteristics in which A. pallidus differs from B. guttulatus are described and illustrated. A short introduction to the ecology of A. pallidus is given and the distribution in Europe is shown. With this new species, 47 millipedes are now known to occur in the Netherlands.
    Keywords: Arthropoda ; Myriapoda ; Diplopoda ; Archiboreoiulus pallidus ; Nederland ; Verspreiding ; Biotopen ; Herkenning ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 42
    facet.materialart.
    Unknown
    In:  Nederlandse Faunistische Mededelingen (01692453) vol.8 (1999) p.67
    Publication Date: 2007-01-09
    Description: Checklist of the Dutch centipedes (Myriapoda: Chilopoda) An updated checklist for the centipedes of the Netherlands is presented. One species, Lithobius subtilis, is new compared with the previous checklist. The updated list will be used for the project ‘The centipedes of the Netherlands’ of the European Invertebrate Survey - Nederland.
    Keywords: Arthropoda ; Myriapoda ; Chilopoda ; Naamlijst ; Nederland ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 43
    facet.materialart.
    Unknown
    In:  Nederlandse Faunistische Mededelingen (01692453) vol.9 (1999) p.11
    Publication Date: 2007-01-09
    Description: Arrenurus boruzkii, een nieuwe watermijt voor Nederland, met opmerkingen over de morfologie (Acari: Hydrachnidia) In 1998 werd de watermijt Arrenurus boruzkii Ssujetow, 1931 voor het eerst in Nederland aangetroffen. Een vrouwtje werd verzameld in een sloot in Overijssel. De morfologische verschillen met Zweedse exemplaren en beschrijvingen in de literatuur worden besproken.
    Keywords: Acari ; Hydrachnidia ; Nederland ; Verspreiding ; Herkenning ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 44
    Publication Date: 2007-01-10
    Description: The influence of recent inundations on the distribution pattern of the isopod Eluma purpurascens in the province of Zeeland (Crustacea: Isopoda: Oniscoidea) Small scale mapping of Eluma purpurascens Budde-Lund, 1885 in the province of Zeeland revealed a remarkable distribution pattern. The species proved to be absent in parts which have been inundated during and after the second world war. This study shows that for the interpretation of distribution patterns the history of the study area should be considered.
    Keywords: Arthropoda ; Crustacea ; Isopoda ; Oniscoidea ; Nederland ; Verspreiding ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 45
    facet.materialart.
    Unknown
    In:  Zoologische Mededelingen (00240672) vol.73, 1-11 (1999) p.63
    Publication Date: 2007-01-23
    Description: During the Rumphius Biohistorical Expedition (RBE) to Ambon, 33 species of swimming crabs were collected in the littoral and upper sublittoral zone by hand on tidal flats, using SCUBA, and using a Holthuis dredge. Lissocarcinus arkati, L. laevis, Charybdis (C.) hellerii, C. (C.) orientalis, C. (C.) variegata, Portunus hastatoides, P. iranjae, P. longispinosus, P. stephensoni, T. chaptalii, T. cooperi, T. stephensoni are recorded at Ambon and in the Moluccas for the first time. The Portunus tenuipes complex is partly revised and P. rugosus sensu Stephenson (1961) is considered a synonym of P. tenuipes De Haan, 1835. A new species, P. pseudotenuipes occurring at Ambon, in the Philippines and off South-East Asia is described. The Ambon fauna includes 55 swimming crab species, while for the Moluccas fauna 70 species are known. This makes Ambon probably one of the best studied local portunid faunas in the Indo-Pacific. According to the RBE collection and literature data, several groups of species with certain habitat preferences are discussed. 1) Upper sublittoral dwellers. 2) Shore dwellers occur in the intertidal zone, mostly on tidal flats, and in the upper sublittoral. 3) Primarily rock, rubble and reefflat dwellers belonged mainly to the genus Thalamita. 4) Symbiotic species of Caphyra are associated with alcyonarians while Lissocarcinus are commensals of anthozoans and echinoderms. A new association was recorded for the first time for Lissocarcinus arkati (with sea urchins), and the association of L. laevis with ceriantharians was confirmed.
    Keywords: Crustacea ; Decapoda ; Brachyura ; Portunidae ; Indonesia ; Ambon ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 46
    facet.materialart.
    Unknown
    In:  Zoologische Mededelingen (00240672) vol.73, 1-11 (1999) p.27
    Publication Date: 2007-01-23
    Description: Twenty-four species of trapeziid crabs, symbionts of scleractinian corals and other colonial cnidarians, are listed from Ambon and other locations throughout Indonesia. Sixteen of these species were collected by the Rumphius Biohistorical Expedition to Ambon (1990). Eight species (Quadrella reticulata Alcock, 1898, Tetraloides heterodactyla (Heller, 1861), Trapezia flavopunctata Eydoux & Souleyet, 1842, T. formosa Smith, 1869, T. garthi Galil, 1983, T. lutea Castro, 1997, T. punctipes Castro, 1997 and T. serenei Odinetz, 1984) are new records for Indonesia. The taxonomic status of Quadrella boopsis, Q. reticulata, Tetralia rubridactyla Garth, 1971 and Trapezia garthi Galil, 1983 are also revised. A key for the identification of the Indonesian species of Quadrella, Tetralia and Trapezia is given.
    Keywords: Crustacea ; Brachyura ; Trapeziidae ; symbiosis ; new records ; Ambon ; Indonesia ; 42.74
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  • 47
    facet.materialart.
    Unknown
    In:  Nederlandse Faunistische Mededelingen (01692453) vol.8 (1999) p.77
    Publication Date: 2007-01-09
    Description: Cylisticus convexus, a rare synanthropic woodlouse in The Netherlands (Crustacea: Isopoda: Cylisticidae) Until recently, the occurrence of Cylisticus convexus (De Geer, 1778) in the Netherlands was uncertain. The only certain old record dates from March 1927, when the species was collected at the coal-shed of the Zoological Museum at Amsterdam. During the last years, two specimens have been collected on semi-natural sites. Both were found on a dike, one near Everdingen, in the province of Gelderland, and one near Ritthem, in the province of Zeeland. These are the first records of C. convexus in the field. Yet the species certainly is very rare in The Netherlands. The most important morphological characteristics of the species are described and illustrated. Some information on the ecology and distribution in Europe is provided.
    Keywords: Crustacea ; Isopoda ; Oniscoidea ; Cylisticus convexus ; Verspreiding ; Herkenning ; Biotopen ; Nederland ; 42.74
    Repository Name: National Museum of Natural History, Netherlands
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  • 48
    ISSN: 0006-3525
    Keywords: folding type-specific secondary structure propensities ; amino acids ; α-helical proteins ; β sheet proteins ; α/β proteins ; α+β proteins ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Folding type-specific secondary structure propensities of 20 naturally occurring amino acids have been derived from α-helical, β-sheet, α/β, and α+β proteins of known structures. These data show that each residue type of amino acids has intrinsic propensities in different regions of secondary structures for different folding types of proteins. Each of the folding types shows markedly different rank ordering, indicating folding type-specific effects on the secondary structure propensities of amino acids. Rigorous statistical tests have been made to validate the folding type-specific effects. It should be noted that α and β proteins have relatively small α-helices and β-strands forming propensities respectively compared with those of α+β and α/β proteins. This may suggest that, with more complex architectures than α and β proteins, α+β and α/β proteins require larger propensities to distinguish from interacting α-helices and β-strands. Our finding of folding type-specific secondary structure propensities suggests that sequence space accessible to each folding type may have differing features. Differing sequence space features might be constrained by topological requirement for each of the folding types. Almost all strong β-sheet forming residues are hydrophobic in character regardless of folding types, thus suggesting the hydrophobicities of side chains as a key determinant of β-sheet structures. In contrast, conformational entropy of side chains is a major determinant of the helical propensities of amino acids, although other interactions such as hydrophobicities and charged interactions cannot be neglected. These results will be helpful to protein design, class-based secondary structure prediction, and protein folding. © 1998 John Wiley & Sons, Inc. Biopoly 45: 35-49, 1998
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  • 49
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 45 (1998), S. 69-83 
    ISSN: 0006-3525
    Keywords: DNA branched junctions ; branch migration ; superhelical torque ; control of DNA structure ; endonuclease VII ; nanomechanical device ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: DNA branched junctions are analogues of Holliday junction recombination intermediates. Partially mobile junctions contain a limited amount of homology flanking the branch point. A partially mobile DNA branched junction has been incorporated into a synthetic double-stranded circular DNA molecule. The junction is flanked by four homologous nucleotide pairs, so that there are five possible locations for the branch point. Two opposite arms of the branched junction are joined to form the circular molecule, which contains 262 nucleotides to the base of the junction. This molecule represents a system whereby torque applied to the circular molecule can have an impact on the junction, by relocating its branch point. Ligation of the molecule produces two topoisomers; about 87% of the product is a relaxed molecule, and the rest is a molecule with one positive supercoil. The position of the branch point is assayed by cleaving the molecule with endonuclease VII. We find that the major site of the branch point in the relaxed topoisomer is at the maximally extruded position in the relaxed molecule. Upon the addition of ethidium, the major site of the branch point migrates to the minimally extruded position. © 1998 John Wiley & Sons, Inc. Biopoly 45: 69-83, 1998
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  • 50
    ISSN: 0006-3525
    Keywords: conformation ; aggregation ; κ-carrageenan ; flow field-flow fractionation ; multiangle light scattering ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relatively novel combination of flow field-flow fractionation (FFF) and multiangle light scattering (MALS) was employed to study a nondegraded κ-carrageenan in different 0.1M salt solutions. The applicability of the technique was tested, and the effects of salt type and salt composition on the molar mass and radius of gyration were studied. A conformational ordering was induced at room temperature by switching the solvent from 0.1M NaCl (coil form) to 0.1M NaI (helix form). An approximate doubling of the average molar mass and an increase in radius of gyration was then observed, in agreement with results obtained previously using size exclusion chromatography-MALS. This increase in size was attributed to conformational ordering and to the formation of double helices. Severe aggregation was observed above 40% CsI in the 0.1M mixed salt solution of CsI and NaI. This was ascribed to the association of helices into large aggregates. For these large associates, having molar masses of several millions, a reversal of the elution order in flow FFF was detected. © 1998 John Wiley & Sons, Inc. Biopoly 45: 85-96 1998
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  • 51
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 45 (1998), S. 119-133 
    ISSN: 0006-3525
    Keywords: conformations of D-alanyl-D-alanine ; β-lactam ; structural overlay ; AMBER force field ; AM1 ; ab initio ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article a conformational analysis of the D-alanyl-D-alanine dipeptide, both charged and neutral, has been carried out. The preferred conformations were determined by means of ab initio and semiempirical quantum, together with empirical force field calculations. The AMBER* force field and the 6-31 + G** and 6-31G** ab initio levels give rise to a coincident minimum energy structure, which, on the other hand, differs from that determined by AM1, 3-21 + G, and 3-21G. The solvent effect on the different charged and neutral conformations have been considered through the AMSOL semiempirical method. A quantification regarding the structural similarities between the different dipeptide conformations and the ampicillin has been performed. The results show that the best overlay is attained by the minimum structure energy obtained by using the 6-31 + G** methodology, which presents a planar amidic nitrogen. © 1998 John Wiley & Sons, Inc. Biopoly 45: 119-133, 1998
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  • 52
    ISSN: 0006-3525
    Keywords: chemical oxidation ; cellulose ; conformational transition ; capillary viscosity ; microcalorimetry ; calcium ions ; gels ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational behavior of different molecular weight fractions of a synthetic C6-oxidized derivative of cellulose were investigated by means of capillary viscometry, CD, and microcalorimetric measurements. Experiments were carried out in the presence of either monovalent or divalent counterions.The experimental data indicated that C6-oxidized cellulose can assume an ordered extended conformation at low ionic strength, induced by the intrachain repulsions of negative charges. This conformation was suggested to be very similar to the fully extended structure of cellulose. In addition to this, upon increasing the ionic strength, a conformational transition of the order-to-disorder type occurred. In fact, the screening of the electrostatic repulsions introduced a number of conformational kinks into the cellulosic backbone, which enabled the polymer to assume a more coiled conformation hence producing less viscous aqueous solutions. © 1998 John Wiley & Sons, Inc. Biopoly 45: 157-163, 1998
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  • 53
    ISSN: 0006-3525
    Keywords: conformational stability ; biological polyelectrolytes ; enthalpy ; entropy ; conformational transitions ; carrageenan ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method is proposed for the determination of the enthalpy and entropy changes of nonionic origin upon conformational transition of linear biopolyelectrolytes in solution. For all transition midpoints, defined by given temperature and ionic strength, the total free energy change of the system is zero, which means that the nonionic contribution to the free energy change is equal in value and opposite in sign to the polyelectrolytic one. The counterion condensation theory of linear polyelectrolytes provides for the appropriate analytical expression to be used in such calculations. Linear plots of the proper functions of the calculated free energy changes vs the proper functions of temperature allows for the determination of the enthalpic and entropic terms of the nonionic free energy change of transition.The method has been applied to the extensive available data of the ion-induced conformational change of κ-carrageenan, a linear sulfated galactan extracted from seaweeds. The method has proved very successful, with the results showing a remarkable convergency of the enthalpy values for different monovalent counterions. On the other hand, the above approach has made it possible to explain the known effect of counterion specificity on the transition by a small difference in the nonionic entropic contributions. © 1998 John Wiley & Sons, Inc. Biopoly 45: 203-216, 1998
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  • 54
    ISSN: 0006-3525
    Keywords: uv resonance Raman spectroscopy ; Raman cross section ; hypochromism ; DNA ; deoxynucleoside ; protein ; aromatic amino acid ; virus assembly ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ultraviolet resonance Raman (UVRR) spectra of H2O and D2O solutions of the nucleoside (dA, dG, dC, dT) and aromatic amino acid (Phe, Trp, Tyr) constituents of DNA viruses have been obtained with laser excitation wavelengths of 257, 244, 238, and 229 nm. Using the 981 cm-1 marker of Na2SO4 as an internal standard, Raman frequencies and scattering cross sections were evaluated for all prominent UVRR bands at each excitation wavelength. The results show that UVRR cross sections of both the nucleosides and amino acids are strongly dependent on excitation wavelength and constitute sensitive and selective probes of the residues. The results provide a library of UVRR marker bands for structural analysis of DNA viruses and other nucleoprotein assemblies. © 1998 John Wiley & Sons, Inc. Biopoly 45: 247-256, 1998
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  • 55
    ISSN: 0006-3525
    Keywords: hemoglobin ; hexagonal bilayer ; Lumbricus ; electron microscopy ; three-dimensional reconstruction ; small-angle x-ray scattering ; three-dimensional models ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The quaternary structure of Lumbricus terrestris hemoglobin was investigated by small-angle x-ray scattering (SAXS). Based on the SAXS data from several independent experiments, a three-dimensional (3D) consensus model was established to simulate the solution structure of this complex protein at low resolution (about 3 nm) and to yield the particle dimensions. The model is built up from a large number of small spheres of different weights, a result of the two-step procedure used to calculate the SAXS model. It accounts for the arrangement of 12 subunits in a hexagonal bilayer structure and for an additional central unit of cylinder-like shape. This model provides an excellent fit of the experimental scattering curve of the protein up to h = 1 nm-1 and a nearly perfect fit of the experimental distance distribution function p(r) in the whole range. Scattering curves and p(r) functions were also calculated for low-resolution models based on 3D reconstructions obtained by cryoelectron microscopy (EM). The calculated functions of these models also provide a very good fit of the experimental scattering curve (even at h 〉 1 nm-1) and p(r) function, if hydration is taken into account and the original model coordinates are slightly rescaled. The comparison of models reveals that both the SAXS-based and the EM-based model lead to a similar simulation of the protein structure and to similar particle dimensions. The essential differences between the models concern the hexagonal bilayer arrangement (eclipsed in the SAXS model, one layer slightly rotated in the EM model), and the mass distribution, mainly on the surface and in the central part of the protein complex. © John Wiley & Sons, Inc. Biopoly 45: 289-298, 1998
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  • 56
    ISSN: 0006-3525
    Keywords: conformational changes ; vicinal glycosylation ; branched α-l-Rhap(1-2)[β-d-Galp(1-3)]-β-d-Glc1-OMe trisaccharide ; parent disaccharides ; hydrogen bond ; isotope effect ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformations of the α-l-Rhap(1-2)-β-d-Glc1-OMe and β-d-Galp(1-3)-β-d-Glc1-OMe disaccharides and the branched title trisaccharide were examined in DMSO-d6 solution by 1H-nmr. The distance mapping procedure was based on rotating frame nuclear Overhauser effect (NOE) constraints involving C- and O-linked protons, and hydrogen-bond constraints manifested by the splitting of the OH nmr signals for partially deuteriated samples. An “isotopomer-selected NOE” method for the unequivocal identification of mutually hydrogen-bonded hydroxyl groups was suggested. The length of hydrogen bonds thus detected is considered the only one motionally nonaveraged nmr-derived constraint. Molecular mechanics and molecular dynamics methods were used to model the conformational properties of the studied oligosaccharides. Complex conformational search, relying on a regular Φ,Ψ-grid based scanning of the conformational space of the selected glycosidic linkage, combined with simultaneous modeling of different allowed orientations of the pendant groups and the third, neighboring sugar residue, has been carried out. Energy minimizations were performed for each member of the Φ,Ψ grid generated set of conformations. Conformational clustering has been done to group the minimized conformations into families with similar values of glycosidic torsion angles. Several stable syn and anti conformations were found for the 1→2 and 1→3 bonds in the studied disaccharides. Vicinal glycosylation affected strongly the occupancy of conformational states in both branches of the title trisaccharide. The preferred conformational family of the trisaccharide (with average Φ,Ψ values of 38°, 17° for the 1→2 and 48°, 1° for the 1→3 bond, respectively) was shown by nmr to be stabilized by intramolecular hydrogen bonding between the nonbonded Rha and Gal residues. © 1998 John Wiley & Sons, Inc. Biopoly 46: 417-432, 1998
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  • 57
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    Biopolymers 46 (1998), S. 489-492 
    ISSN: 0006-3525
    Keywords: refractive index increment ; proteins ; solvent ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The refractive index increment of a protein solution is a property not only of the protein, but also of the solvent. This is demonstrated theoretically and confirmed experimentally using analytical interferometry. © 1998 John Wiley & Sons, Inc. Biopoly 46: 489-492, 1998
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  • 58
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    Biopolymers 47 (1998), S. 1-1 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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  • 59
    ISSN: 0006-3525
    Keywords: hepatitis A ; synthetic peptides ; CD ; liposomes ; computational study ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present study was undertaken to examine the structural features that may be important to explain the immunogenicity of the (110-121) peptide sequence (FWRGDLVFDFQV) of VP3 capsid protein of hepatitis A virus. A conformational analysis of the preferred conformations by CD and molecular mechanics was carried out. Present results suggest that the interaction with liposomes as biomembrane model induces and stabilizes the amphipathic β-structure of the peptide.To study the contribution of amino acid replacements at the RGD tripeptide as well as the influence of the peptide chain length on peptide conformation, solid-phase peptide synthesis of several peptide analogs was carried out and the peptide conformation was studied using CD spectroscopy. The results show that the RGD sequence is necessary to induce the β-structure in the presence of liposomes. © 1998 John Wiley & Sons, Inc. Biopoly 45: 479-492, 1998
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  • 60
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    Biopolymers 46 (1998), S. 31-37 
    ISSN: 0006-3525
    Keywords: DNA liquid crystals ; DNA fragments ; screened Coulomb interactions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The critical volume fractions pertaining to the formation of DNA liquid crystals were obtained from polarization microscopy, 31P-nmr, and phase separation experiments. The DNA length (approximately one to two times the persistence length 50 nm), ionic strength, and counterion variety dependencies are reported. The cholesteric-isotropic transition is interpreted in terms of the coexistence equations, which are derived from the solution free energy including orientational entropy and excluded volume effects. With the wormlike chain as reference system, the electrostatic contribution to the free energy is evaluated as a thermodynamic perturbation in the second virial approximation with a Debye-Hückel potential of mean force. The hard core contribution has been evaluated with scaled particle theory and/or a simple generalization of the Carnahan-Starling equation of state for hard spheres. For sufficiently high ionic strengths, the agreement is almost quantitative. At lower amounts of added salt deviations are observed, which are tentatively attributed to counterion screening effects. The contour length dependence agrees with a DNA persistence length 50 nm. © 1998 John Wiley & Sons, Inc. Biopoly 46: 31-37, 1998
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  • 61
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    Biopolymers 46 (1998), S. 245-252 
    ISSN: 0006-3525
    Keywords: gelatin ; gelation ; atomic force microscopy ; interfacial rheology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gelation of gelatin under various conditions has been followed by atomic force microscopy (AFM) with the objective of understanding more fully the structure formed during the gelation process. AFM images were obtained of the structures formed from both the bulk sol and in surface films during the onset of gelation. While gelation occurred in the bulk sol, the extent of helix formation was monitored by measurements of optical rotation, and the molecular aggregation was imaged by AFM. Interfacial gelatin films formed at the air-water interface were also studied. Measurements of surface tension and surface rheology were made periodically and Langmuir-Blodgett films were drawn from the interface to allow AFM imaging of the structure of the interfacial layer as a function of time. Structural studies reveal that at low levels of helical content the gelatin molecules assemble into aggregates containing short segments of dimensions comparable to those expected for gelatin triple helices. With time larger fibrous structures appear whose dimensions suggest that they are bundles of triple helices. As gelation proceeds, the number density of fibers increases at the expense of the smaller aggregates, eventually assembling into a fibrous network. The gel structure appears to be sensitive to the thermal history, and this is particularly important in determining the structure and properties of the interfacial films. © 1998 John Wiley & Sons, Inc. Biopoly 46: 245-252, 1998
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  • 62
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    Biopolymers 48 (1998), S. 65-81 
    ISSN: 0006-3525
    Keywords: nucleotide analogue interference mapping ; phosphorothioate ; group I intron ; interference suppression ; RNA ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this review I will outline several chemogenetic approaches used to determine the chemical basis of large ribozyme function and structure. The term chemogenetics was first used to describe site-specific functional group modification experiments in the analysis of DNA-protein interactions. Within the past few years equivalent experiments have been performed on large catalytic RNAs using both single-site substitution and interference mapping techniques with nucleotide analogues. While functional group mutagenesis is an important aspect of a chemogenetic approach, chemical correlates to genetic revertants and suppressors must also be realized for the genetic analogy to be intellectually valid and experimentally useful. Several examples of functional group revertants and suppressors have now been obtained within the Tetrahymena group I ribozyme. These experiments define an ensemble of tertiary hydrogen bonds that have made it possible to construct a detailed model of the ribozyme catalytic core. The model includes a functionally important monovalent metal ion binding site, a wobble-wobble receptor motif for helix-helix packing interactions, and a minor groove triple helix. © 1998 John Wiley & Sons, Inc. Biopoly 48: 65-81, 1998
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  • 63
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    Biopolymers 48 (1998), S. 83-96 
    ISSN: 0006-3525
    Keywords: nucleic acid ; disulfide cross-link ; structure ; dynamics ; stability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this review I discuss straightforward and general methods to modify nucleic acid structure with disulfide cross-links. A motivating factor in developing this chemistry was the notion that disulfide bonds would be excellent tools to probe the structure, dynamics, thermodynamics, folding, and function of DNA and RNA, much in the way that cystine cross-links have been used to study proteins. The chemistry described has been used to synthesize disulfide cross-linked hairpins and duplexes, higher order structures like triplexes, nonground-state conformations, and tRNAs. Since the cross-links form quantitatively by mild air oxidation and do not perturb either secondary or tertiary structure, this modification should prove quite useful for the study of nucleic acids. © 1998 John Wiley & Sons, Inc. Biopoly 48: 83-96, 1998
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  • 64
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    Biopolymers 48 (1998), S. 113-135 
    ISSN: 0006-3525
    Keywords: divalent cations ; magnesium ; RNA ; ion binding ; RNA folding ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Divalent cations, like magnesium, are crucial for the structural integrity and biological activity of RNA. In this article, we present a picture of how magnesium stabilizes a particular folded form of RNA. The overall stabilization of RNA by Mg2+ is given by the free energy of transferring RNA from a reference univalent salt solution to a mixed salt solution. This term has favorable energetic contributions from two distinct modes of binding: diffuse binding and site binding. In diffuse binding, fully hydrated Mg ions interact with the RNA via nonspecific long-range electrostatic interactions. In site binding, dehydrated Mg2+ interacts with anionic ligands specifically arranged by the RNA fold to act as coordinating ligands for the metal ion. Each of these modes has a strong coulombic contribution to binding; however, site binding is also characterized by substantial changes in ion solvation and other nonelectrostatic contributions. We will show how these energetic differences can be exploited to experimentally distinguish between these two classes of ions using analyses of binding polynomials. We survey a number of specific systems in which Mg2+-RNA interactions have been studied. In well-characterized systems such as certain tRNAs and some rRNA fragments these studies show that site-bound ions can play an important role in RNA stability. However, the crucial role of diffusely bound ions is also evident. We emphasize that diffuse binding can only be described rigorously by a model that accounts for long-range electrostatic forces. To fully understand the role of magnesium ions in RNA stability, theoretical models describing electrostatic forces in systems with complicated structures must be developed. © 1999 John Wiley & Sons, Inc. Biopoly 48: 113-135, 1998
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  • 65
    ISSN: 0006-3525
    Keywords: 1H-nmr ; molecular modeling ; peptaibol ; peptide-lipid interaction ; sodium dodecyl sulfate micelles ; trichorzianin TA VII ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trichorzianin TA VII, Ac0 U1 A2 A3 U4 J5 Q6 U7 U8 U9 S10 L11 U12 P13 V14 U15 I16 Q17 Q18 Fol19, is a nonadecapeptide member of the peptaibol antibiotics biosynthesized by Trichoderma soil fungi, which is characterized by a high proportion of the α,α-dialkylated amino acids, α-aminoisobutyric acid (Aib, U) and isovaline (Iva, J), an acetylated N-terminus and a C-terminal phenylalaninol (Pheol, Fol). The main interest in such peptides stems from their ability to interact with phospholipid bilayers and form voltage-dependent transmembrane channels in planar lipid bilayers. In order to provide insights into the lipid-peptide interaction promoting the voltage gating, the conformational study of TA VII in the presence of perdeuterated sodium dodecyl sulfate (SDS-d25) micelles has been carried out. 1H sequential assignments have been performed with the use of two-dimensional homo- and -heteronuclear nmr techniques including double quantum filtered correlated spectroscopy, homonuclear Hartmann-Hahn, nuclear Overhauser effect spectroscopy, 1H-13C heteronuclear single quantum correlation, and heteronuclear multiple bond correlation. Conformational parameters, such as 3JNHCαH coupling constants, temperature coefficients of amide protons (Δδ/ΔTNH) and quantitative nuclear Overhauser enhancement data, lead to detailed structural information. Ninety-eight three-dimensional structures consistent with the nmr data were generated from 231 interproton distances and six Φ dihedral angle restraints, using restrained molecular dynamics and energy minimization calculations. The average rms deviation between the 98 refined structures and the energy-minimized average structure is 0.59 Å for the backbone atoms. The structure of trichorzianin TA VII associated with SDS micelles, as determined by these methods, is characterized by two right-handed helical segments involving residues 1-8 and 11-19, linked by a β-turn that leads to an angle about 90°-100° between the two helix axes; residues 18 and 19 at the end of the C-terminal helix exhibit multiple conformations. © 1998 John Wiley & Sons, Inc. Biopoly 46: 75-88, 1998
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  • 66
    ISSN: 0006-3525
    Keywords: 9-hydroxyellipticine ; DNA ; CD ; linear dichroism ; resonance light scattering ; intercalation ; drug-drug interactions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding of 9-hydroxyellipticine to calf thymus DNA, poly[d(A-T)]2, and poly-[d(G-C)]2 has been studied in detail by means of CD, linear dichroism, resonance light scattering, and molecular dynamics. The transition moment polarizations of 9-hydroxyelliptiycine were determined in polyvinyl alcohol stretched film. Spectroscopic solution studies of the DNA/drug complex are combined with theoretical CD calculations using the final 50 ps of a series of molecular dynamics simulations as input. The spectroscopic data shows 9-hydroxyellipticine to adopt two main binding modes, one intercalative and the other a stacked binding mode involving the formation of drug oligomers in the DNA major groove. Analysis of the intercalated binding mode in poly[d(A-T)]2 suggests the 9-hydroxyellipticine hydroxyl group lies in the minor groove and hydrogen bonds to water with the pyridine ring protruding into the major groove. The stacked binding mode was examined using resonance light scattering and it was concluded that the drug was forming small oligomer stacks rather than extended aggregates. Reduced linear dichroism measurements suggested a binding geometry that precluded a minor groove binding mode where the plane of the drug makes a 45° angle with the plane of the bases. Thus it was concluded that the drug stacks in the major groove. No obvious differences in the mode of binding of 9-hydroxyellipticine were observed between different DNA sequences; however, the stacked binding mode appeared to be more favorable for calf thymus DNA and poly[d(G-C)]2 than for poly[d(A-T)]2, an observation that could be explained by the slightly greater steric hindrance of the poly[d(A-T)]2 major groove. A strong concentration dependence was observed for the two binding modes where intercalation is favored at very low drug load, with stacking interactions becoming more prominent as the drug concentration is increased. Even at DNA : drug mixing ratios of 70:1 the stacked binding mode was still important for GC-rich DNAs. © 1998 John Wiley & Sons, Inc. Biopoly 46: 127-143, 1998
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  • 67
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    Biopolymers 46 (1998), S. 169-179 
    ISSN: 0006-3525
    Keywords: macromolecular carriers ; drug targeting and delivery ; branched chain synthetic polypeptides ; membrane-synthetic polypeptide interaction ; lipid monolayers/bilayers ; polymer therapeutics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The surface properties at the air/water interface and the interaction of branched chain polymeric polypeptides with a general formula poly[Lys-(DL-Alam-X1)], where X = Π (AK), Ser (SAK), or Glu (EAK), with phospholipids were investigated. Polylysine derivatives with polycationic (SAK, AK) or amphoteric (EAK) were capable to spread and form stable monomolecular layers. The stability of monolayers at the air/water interface was dependent on the side-chain terminal amino acid residue of polymers and can be described by SAK 〈 AK 〈 EAK order. The area per amino acid residue values calculated from compression isotherms were in the same range as compared to those of linear poly-α-amino acids and proteins. Moreover, these polymers interact with phospholipid monomolecular layers composed of dipalmitoyl phosphatidyl choline (DPPC) or DPPC/PG (PG: phosphatidyl glycerol; 95/5, mol/mol). Data obtained from compression isotherms of phospholipids spread on aqueous polymer solutions at different initial surface pressure indicated that insertion into lipid monolayers for SAK or AK is more pronounced than for EAK. The interaction between branched polypeptides and phospholipid membranes was further investigated using lipid bilayers with DPPC/PG and fluorescent probes located either at the polar surface [1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) sodium anilino naphthalene sulfonate (ANS)] or within the hydrophobic core (DPH) of the liposome. Changes in fluorescence intensity and in polarization were observed when TMA-DPH or ANS, but not DPH were used. Comparative data also indicate that all three polymers interact only with the outer surface of the bilayer, but even the most marked penetration of polycationic polypeptide (SAK) did not result in alteration of the ordered state of the alkyl chains in the bilayer. Taken together, data obtained from mono- or bilayer experiments suggest that the interaction between branched polymers and phospholipids are highly dependent on the charge properties (Ser vs Glu) and on the identity (Ser vs Ala) of side-chain terminating amino acids. The binding of polymers to the model membranes could be mainly driven by electrostatic forces, but the significant role of hydrophilic properties in case of SAK cannot be excluded. © 1998 John Wiley & Sons, Inc. Biopoly 46: 169-179, 1998
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  • 68
    ISSN: 0006-3525
    Keywords: Cα,α-dialkylated glycines ; molecular dynamics ; geometry and conformation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relationship between the local backbone conformation and bond angles at Cα of symmetrically substituted Cα,α-dialkylated glycines (Cα,α-dimethylglycine or α-aminoisobutyric acid, Aib; Cα,α-diethylglycine, Deg; Cα,α-di-n-propylglycine, Dpg) has been investigated by molecular dynamics (MD) simulation adopting flat bottom harmonic potentials, instead of the usual harmonic restraints, for the Cα bond angles. The MD simulations show that the Cα bond angles are related to the local backbone conformation, irrespectively of the side-chain length of Aib, Deg, and Dpg residues. Moreover, the N-Cα-C′ (τ) angle is the most sensitive conformational parameter and, in the folded form, is always larger and more flexible than in the extended one. © 1998 John Wiley & Sons, Inc. Biopoly 46: 239-244, 1998
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  • 69
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    Biopolymers 46 (1998), S. 319-327 
    ISSN: 0006-3525
    Keywords: methionine ligation ; parathyroid hormones ; biomimetic ligation ; S-methylation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In biological systems, both proteolysis and aminolysis of amide bonds produce activated intermediates through acyl transfer reactions either inter- or intramolecularly. Protein splicing is an illustrative example that proceeds through a series of catalyzed acyl transfer reactions and culminates at an O- or S-acyl intermediate. This intermediate leads to an uncatalyzed acyl migration to form an amide bond in the spliced product. A ligation method mimicking the uncatalyzed final steps in protein splicing has been developed utilizing the acyl transfer amide-bond feature for the blockwise coupling of unprotected, free peptide segments at methionine (Met). The latent thiol moiety of Met can be exploited using homocysteine at the α-amino terminal position of a free peptide for transthioesterification with another free peptide containing an α-thioester to give an S-acyl intermediate. A subsequent, proximity-driven S- to N-acyl migration of this acyl intermediate spontaneously rearranges to form a homocysteinyl amide bond. S-methylation with excess p-nitrobenezensulfonate yields Met at the ligation site. The methionine ligation is selective and orthogonal, and is usually completed within 4 h when performed at slightly basic pH and under strongly reductive conditions. No side reactions due to acylation were observed with any other α-amines of both peptide segments as seen in the synthesis of parathyroid hormone peptides. Furthermore, cyclic peptide can also be obtained through the same strategy by placing both homocysteine at the amino terminus and the thioester at the carboxyl terminus in an unprotected peptide precursor. These biomimetic ligation strategies hold promise for engineering novel peptides and proteins. © 1998 John Wiley & Sons, Inc. Biopoly 46: 319-327, 1998
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  • 70
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    Biopolymers 46 (1998), S. 359-373 
    ISSN: 0006-3525
    Keywords: boundary element method ; DNA electrophoresis ; electrophoretic mobility of DNA ; free solution electrophoretic mobility of DNA ; ion relaxation, DNA electrophoresis ; modeling electrophoresis of polyions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Boundary element methods are used to model the free solution electrophoretic mobility of short DNA fragments. The Stern surfaces of the DNA fragments are modeled as plated cylinders that reproduce translational and rotational diffusion constants. The solvent-accessible and ion-accessible surfaces are taken to be coincident with the Stern surface. The mobilities are computed by solving simultaneously the coupled Navier-Stokes, Poisson, and ion-transport equations. The equilibrium electrostatics are treated at the level of the full Poisson-Boltzmann equation and ion relaxation is included. For polyions as highly charged as short DNA fragments, ion relaxation is substantial. At .11 M KCl, the simulated mobilities of a 20 base pair DNA fragment are in excellent agreement with experiment. At .04 M Tris acetate, pH = 8.0, the simulated mobilities are about 10-15% higher than experimental values and this discrepancy is attributed to the relatively large size of the Tris counterion. The length dependence of the mobility at .11 M KCl is also investigated. Earlier mobility studies on lysozyme are reexamined in view of the present findings. In addition to electrophoretic mobilities, the effective polyion charge measured in steady state electrophoresis and its relationship to the preferential interaction parameter γgG is briefly considered. © 1998 John Wiley & Sons, Inc. Biopoly 46: 359-373, 1998
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  • 71
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    Biopolymers 45 (1998), S. 341-346 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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  • 72
    ISSN: 0006-3525
    Keywords: diffusional encounter ; Brownian dynamics ; average Boltzmann factor ; acetylcholinesterase ; Poisson-Boltzmann ; electrostatics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The utility of the average Boltzmann factor around the active site of an enzyme as the predictor of the electrostatic enhancement of the substrate binding rate is tested on a set of data on wild-type acetylcholinesterase and 18 charge mutants recently obtained by Brownian dynamics simulations. A good correlation between the average Boltzmann factors and the substrate binding rate constants is found. The effects of single charge mutations on both the Boltzmann factor and the substrate binding rate constant are modest, i.e., 〈5 fold increase or decrease. This is consistent with the experimental results of Shafferman et al. but does not support their suggestion that the overall rate of the catalytic reaction is not limited by the diffusional encounter of acetylcholinesterase and its substrate. © 1998 John Wiley & Sons, Inc. Biopoly 45: 355-360, 1998
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  • 73
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    Biopolymers 45 (1998), S. 469-478 
    ISSN: 0006-3525
    Keywords: molecular dynamics ; hydrated proteins ; crystal structures ; density distributions ; globular proteins ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using molecular dynamics simulations of fully hydrated proteins and analysis of crystal structures contained in the Protein Data Bank, we develop a transferable set of perpendicular radial distribution functions for water molecules around globular proteins. These universal functions may be used to reconstruct the unique three-dimensional solvent density distribution around every individual protein with a modest error. We discuss potential applications of this solvent treatment in protein x-ray crystallographic refinements and in theoretical modeling. We also present a fast, grid-based algorithm for construction of the perpendicular solvent density distributions. © 1998 John Wiley & Sons, Inc. Biopoly 45: 469-478, 1998
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  • 74
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    Biopolymers 47 (1998), S. 23-29 
    ISSN: 0006-3525
    Keywords: independently folded polypeptide motifs ; miniproteins ; natural target domains ; BBA motif ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper we present a redesign strategy for the development of uniquely folded polypeptide motifs of less than 40 residues. These mini proteins are based on natural target domains, including the zinc finger domains (BBA motif) Nomenclature corresponds to the defined elements of secondary structure, beginning at the N-terminus of the peptide. Roman lettering refers to a specific motif while Greek characters correspond to the elements of secondary structure within that motif. and the disulfide-rich snake and scorpion toxins (BBB motif). These motifs are designed to act as the molecular framework for the construction of novel functional polypeptides. We will explore the structural determinants of the folded BBA motif, inspired by the zinc finger peptides, in relation to the redesign process. © 1998 John Wiley & Sons, Inc. Biopoly 47: 23-29, 1998
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  • 75
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    Biopolymers 47 (1998), S. 75-81 
    ISSN: 0006-3525
    Keywords: ion channel ; synthetic peptide ; de novo design ; template-assembled synthetic proteins ; supramolecular assembly ; membrane protein ; planer lipid bilayers ; amphiphilic peptide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To create ion channel function by synthetic peptides is a challenge in the de novo design of artificial membrane proteins. Amphiphilic α-helical motifs of ∼ 20 amino acid residues to span lipid bilayers are most often used for the creation of peptide ion channels. Template molecules to tether helical peptides have been employed to obtain more organized pore structures. Approaches to form molecular assembly of peptides in the membranes by hydrogen bonding have been also investigated. We have developed approaches to assemble helices with individual amino acid sequences to construct artificial helical proteins. Using one of these approaches, four helices corresponding to the voltage sensor segments (S4 in repeat I-IV) of the sodium channel were assembled on a peptide template to give a protein having ion channel activity with rectification. © 1998 John Wiley & Sons, Inc. Biopoly 47: 75-81, 1998
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  • 76
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    Biopolymers 47 (1998), S. 127-142 
    ISSN: 0006-3525
    Keywords: collagen mimetics ; triple helix ; peptoid ; template ; biophysics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Collagen peptidomimetics have been synthesized as an alternative to natural collagen. The incorporation of unnatural residues such as peptoids in the collagen sequences can demonstrate potent and specific biological activity and enhance the biostability against enzymatic degradation. Furthermore, the use of achiral peptoids simplifies synthetic strategies by reducing racemization problems. The peptoid residue N-isobutylglycine (Nleu) has been successfully incorporated into a series of collagen mimetics composed of Gly-Pro-Nleu, Gly-Nleu-Pro, and Gly-Nleu-Nleu. The discovery of template-assembled collagen mimetics and metal binding ability has laid the foundation for new opportunities in the design of novel collagen mimetic complexes. This review summarizes the synthesis and integrated biophysical analyses of the structures of these collagen mimetics. Solid phase segment condensation techniques have been utilized for the synthesis of the single chain and template-assembled analogues. The characterization of the collagen-like structures has been established by temperature-dependent optical rotation measurements, CD, NMR spectroscopy, and molecular modelling simulations. © 1998 John Wiley & Sons, Inc. Biopoly 47: 127-142, 1998
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  • 77
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    Keywords: non-natural amino acid ; peptide ; squarylium dye ; thin film ; poly(3-methylthiophene) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We designed a polypeptide that behaves as a photodevice by using a non-natural amino acid with replacement of an α-hydrogen by a squarylium dye and succeeded in syntheses of the non-natural amino acid derivative containing a squarylium and its peptide with trialanine Ala-Ala-Ala. Strong dye-dye interactions were confirmed by absorption and CD spectra for the peptide in 2,2,2-trifluoroethanol solution and in water suspension. The non-natural amino acid derivative could be deposited onto a PMeT/Au electrode by the micelle disruption method. © 1998 John Wiley & Sons, Inc. Biopoly 47: 179-183, 1998
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  • 78
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    Biopolymers 47 (1998), S. 263-263 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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  • 79
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    Keywords: electrostatically driven Monte Carlo method ; cluster analysis ; global energy minimum ; perturbed conformations ; conformational space ; lowest energy conformations ; polypeptide chain ; melittin, membrane-bound portion ; Empirical Conformational Energy Program for Peptides 3 ; annealing methods ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrostatically driven Monte Carlo (EDMC) method has been greatly improved by adding a series of new features, including a procedure for cluster analysis of the accepted conformations. This information is used to guide the search for the global energy minimum. Alternative procedures for generating perturbed conformations to sample the conformational space were also included. These procedures enhance the efficiency of the method by generating a larger number of low-energy conformations.The improved EDMC method has been used to explore the conformational space of a 20-residue polypeptide chain whose sequence corresponds to the membrane-bound portion of melittin. The ECEPP/3 (Empirical Conformational Energy Program for Peptides) algorithm was used to describe the conformational energy of the chain. After an exhaustive search involving 14 independent runs, the lowest energy conformation (LEC) (-91.0 kcal/mol) of the entire study was encountered in four of the runs, while conformations higher in energy by no more than 1.8 kcal/mol were found in the remaining runs with the exception of one of them (run 8). The LEC is identical to the conformation found recently by J. Lee, H.A. Scheraga, and S. Rackovsky [(1998) “Conformational Analysis of the 20-Residue Membrane-Bound Portion of Melittin by Conformational Space Annealing,” Biopolymers, Vol. 46, pp. 103-115] as the lowest energy conformation obtained in their study using the conformational space annealing method. These results suggest that this conformation corresponds to the global energy minimum of the ECEPP/3 potential function for this specific sequence; it also appears to be the conformation of lowest free energy. © 1998 John Wiley & Sons, Inc. Biopoly 46: 117-126, 1998
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    Biopolymers 46 (1998), S. 195-200 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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  • 81
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    Biopolymers 46 (1998), S. 201-214 
    ISSN: 0006-3525
    Keywords: band broadening ; dispersion ; DNA ; gels ; electrophoresis ; fluorescence recovery ; photobleaching ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We determined quantitatively the band broadening effect during gel electrophoresis by measuring the longitudinal dispersion coefficient Dx, with a fluorescence recovery after photobleaching setup, coupled to an electrophoretic cell. We carried out measurements as a function of the electric field, the average pore size, and the molecular length of DNA fragments. Our results are in good agreement with the predictions of the biased reptation model with fluctuations described by T. A. Duke et al. [(1992) Physics Review Letters, vol. 69, pp. 3260-3263]. This agreement is observed on single-stranded DNA [persistence length ≅ 4 nm; B. Tinland et al. (1997) Macromolecules, vol. 30, pp. 5763-5765] in polyacrylamide gels and on double-stranded DNA (persistence length ≅ 50 nm) in agarose gels, two systems where the ratio between the average pore size and the Kuhn length is larger than 1. © 1998 John Wiley & Sons, Inc. Biopoly 46: 201-214, 1998
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  • 82
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    Biopolymers 46 (1998), S. 403-415 
    ISSN: 0006-3525
    Keywords: molecular dynamics ; DNA curvature ; DNA flexibility ; TATA box functionality ; TATA box binding protein (TBP) ; TBP recognition ; TBP binding ; TBP transcriptional activation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four 1.5 ns molecular dynamics (MD) simulations were performed on the d(GCTATAAAAGGG) · d(CCCTTTTATAGC) double helix dodecamer bearing the Adenovirus major late promoter TATA element and three iso-composition mutants for which physical and biochemical data are available from the same laboratory. Three of these DNA sequences experimentally induce tight binding with the TATA box binding protein (TBP) and induce high transcription rates; the other DNA sequence induces much lower TBP binding and transcription. The x-ray crystal structures have previously shown that the duplex DNA in DNA-TBP complexes are highly bent. We performed and analyzed MD simulations for these four DNAs, whose experimental structures are not available, in order to address the issue of whether inherent DNA structure and flexibility play a role in establishing these observed preferences. A comparison of the experimental and simulated results demonstrated that DNA duplex sequence-dependent curvature and flexibility play a significant role in TBP recognition, binding, and transcriptional activation. © 1998 John Wiley & Sons, Inc. Biopoly 46: 403-415, 1998
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  • 83
    ISSN: 0006-3525
    Keywords: vibrational CD ; solution conformation ; alanine oligopeptides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution conformation of a number of small, linear alanine oligomers was investigated via ir (or vibrational) CD (VCD). We find that these oligopeptides assume distinct solution conformations that depend primarily on chain lengths, and to a lesser degree on temperature, ionic strength, and pH. As expected, the longer chain oligomers exhibit more distinct VCD features and, presumably, more stable solution structures. At the level of the hexamer, however, aggregation of the peptide occurs. The fast time scale of VCD allows solution structures to be detected that may not be observable using slower techniques such as various forms of nmr spectroscopy. The VCD results reported here confirm that it is generally possible to obtain conformational information for small, linear homo- and heterooligopeptides via VCD spectroscopy. In this respect, the sensitivity of VCD is similar to that of electronic CD. Furthermore, the temperature dependence of the VCD results indicate that at elevated temperatures, the increasing number of conformational states results in a loss of discernible conformers, and consequently, a broadening and weakening of the VCD features. © 1998 John Wiley & Sons, Inc. Biopoly 46: 455-463, 1998
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  • 84
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    Biopolymers 47 (1998), S. 5-22 
    ISSN: 0006-3525
    Keywords: hemoproteins ; model systems ; miniaturized proteins ; mimochromes ; helix structures ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present paper highlights and reviews current research in the field of hemoprotein models. Hemoproteins have been extensively studied in order to understand structure-function relationships, and to design new molecules with desired functions. A wide number of synthetic analogues have been developed, using quite different approaches. They differ in molecular structures, ranging from simple meso-substituted tetraaryl-metalloporphyrins and peptide-porphyrin conjugates.In this paper we summarize the state of the art on peptide based hemoprotein models. We also report here the approach used by us to develop a new class of molecules, named mimochromes. They can be regarded as miniaturized hemoproteins, because mimochromes are low molecular weight compounds with some structural and functional properties common to those of the parent high molecular weight protein. The basic structure of mimochromes is a deuteroporphyrin ring covalently linked to two helical peptide chains. Two molecules of this series have been fully characterized. All the information derived from their structural analysis has been applied to the design of new analogues with additional functions. © 1998 John Wiley & Sons, Inc. Biopoly 47: 5-22, 1998
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  • 85
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    Biopolymers 46 (1998), S. 503-516 
    ISSN: 0006-3525
    Keywords: discrete charge model of DNA ; dielectric cylinder in water ; effective dielectric constant ; salt effects ; Debye shielding factor ; potential variations in DNA surface ; Boltzmann averaged bending angles ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have studied electrostatic properties of DNA with a discrete charge model consisting of a cylindrical dielectric core with a radius of 8 Å and a dielectric constant Di = 4, surrounded by two helical strings of phosphate point charges at 10 Å from the axis, immersed in an aqueous medium with dielectric constant Dw = 78.54. Eliminating the dielectric core makes potentials in the phosphate surface less negative by about 0.5 kT/e. Salt effects are evaluated for the model without a dielectric core, using the shielded Coulomb potential. Smearing the phosphate charges increases their potential by about 2.5 kT/e, due mostly to the self-potential of the smeared charge. Potentials in the center of the minor and major grooves vary less than 0.02 kT/e along their helical path. The potential in the center of the minor groove is from 1.0 to 1.7 kT/e, more negative than in the center of the major groove, depending on dielectric core and salt concentration. So multivalent cations and also larger cationic ligands, such as some antibiotics, are likely to adsorb in the minor groove, in agreement with earlier computations by A. and B. Pullman. Dielectric effects on the surface potential and the local potential variations are found to be relatively small. Bending of DNA is studied by placing a multivalent cation, MZ+, in the center of the minor or major groove, curving DNA around it for a certain length, and calculating the free energy difference between the bent and the straight configuration. Boltzmann averaged bending angles, 〈β〉, are found to be maximal in 0.03M monovalent salt, for a length of about 50 or 25 Å of curved DNA when an MZ+ ion is adsorbed in the minor or the major groove, respectively. When the dielectric constant of water is used throughout the calculation, we find maximal bends of 〈β〉 = 11° for M2+ and 〈β〉 = 16° for M3+ in the minor groove, 〈β〉 = 13° for M3+ in the major groove. The absence of bends in DNA adsorbed to mica in the presence of Mg salts supports the role of Mg2+ in “ion bridging” between DNA and mica. The treatment of the effective dielectric constant between two points outside a dielectric cylinder in water is appended. © 1998 John Wiley & Sons, Inc. Biopoly 46: 503-516, 1998
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  • 86
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    Biopolymers 47 (1998), S. 63-73 
    ISSN: 0006-3525
    Keywords: protein de novo design ; novel macromolecules ; topological templates ; Template Assembled Synthetic Proteins (TASP) ; biosensors ; protein folding ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ultimate goal in protein de novo design is the creation of novel macromolecules with tailor-made receptor, sensory, and catalytic functions. Despite considerable progress in understanding basic rules of secondary structure formation and protein stability, the well-known protein folding problem is still far from being solved and, in general, only a limited number of designed proteins are folded uniquely. In this article the state-of-the-art in protein design is demonstrated on some selected examples, indicating that the construction of protein-like macromolecules mimicking some essential features of natural proteins seems to be within reach. Thus, protein design and mimicry has become an interdisciplinary challenge with most intriguing perspectives. © 1998 John Wiley & Sons, Inc. Biopoly 47: 63-73, 1998
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  • 87
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    Biopolymers 47 (1998), S. 451-463 
    ISSN: 0006-3525
    Keywords: bacteria ; antibiotics ; linear amphipathic α-helical antimicrobial peptides ; peptide-lipid interactions ; membrane permeation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The increasing resistance of bacteria to conventional antibiotics resulted in a strong effort to develop antimicrobial compounds with new mechanisms of action. Antimicrobial peptides seem to be a promising solution to this problem. Many studies aimed at understanding their mode of action were described in the past few years. The most studied group includes the linear, mostly α-helical peptides. Although the exact mechanism by which they kill bacteria is not clearly understood, it has been shown that peptide-lipid interactions leading to membrane permeation play a role in their activity. Membrane permeation by amphipathic α-helical peptides can proceed via either one of the two mechanisms: (a) transmembrane pore formation via a “barrel-stave” mechanism; and (b) membrane destruction/solubilization via a “carpet-like” mechanism. The purpose of this review is to summarize recent studies aimed at understanding the mode of action of linear α-helical antimicrobial peptides. This review, which is focused on magainins, cecropins, and dermaseptins as representatives of the amphipathic α-helical antimicrobial peptides, supports the carpet-like rather the barrel-stave mechanism. That these peptides vary with regard to their length, amino acid composition, and net positive charge, but act via a common mechanism, may imply that other linear antimicrobial peptides that share the same properties also share the same mechanism. © 1999 John Wiley & Sons, Inc. Biopoly 47: 451-463, 1998
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    Biopolymers 48 (1998), S. 39-55 
    ISSN: 0006-3525
    Keywords: modified nucleotides ; site-specific probes ; RNA structure ; RNA function ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modified nucleotides can be incorporated site specifically into RNA by the use of total chemical synthesis as well as by use of a variety of recombinant RNA techniques. The range of nucleotide analogues includes modifications to base, sugar, and phosphate for structure-function analysis and for cross-linking studies as well as to answer specific mechanistic questions in RNA catalysis. We describe how RNA containing site-specific modifications are prepared, concentrating in particular on routes involving chemically synthesized oligoribonucleotides, and give examples of their application in studies of the hammerhead and hairpin ribozymes. © 1998 John Wiley & Sons, Inc. Biopoly 48: 39-55, 1998
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    Biopolymers 48 (1998), S. 29-37 
    ISSN: 0006-3525
    Keywords: amide synthase ; catalytic antibodies ; Diels-Alderase ; ideal catalyst platform ; in vitro selection ; Lewis acid ; modified uridines ; modified RNA ; ribozymes ; SELEX ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this manuscript the catalytic ability of RNA is examined and compared to other biopolymers. Despite having considerably fewer catalytically enabling properties when compared to proteins, the power of in vitro selection has allowed for RNA and DNA catalysts to be isolated. RNA catalysis has been expanded by incorporating modified bases to enrich the structural and functional diversity of RNA. Successful examples of new RNA chemistry using base modifications include carbon-carbon bond forming reactions and creation of highly specific active sites that are capable of recognizing small organic molecules without the need for nucleic acid templating or intercalation. In fact, the scope of functional modifications available for use in the RNA platform may eventually surpass those that are found in proteins and there are already hints that well chosen modifications allow nucleic acid catalysts to take advantage of mechanisms not available to selected protein catalysts for similar reactions. The chemical versatility of RNA is just emerging and future research directions will likely entail more creative methods for functional modification that will lead to new catalysts. © 1998 John Wiley & Sons, Inc. Biopoly 48: 29-37, 1998
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    Biopolymers 48 (1998), S. 137-153 
    ISSN: 0006-3525
    Keywords: RNA ; pseudoknot ; Turnip Yellow Mosaic Virus ; Mouse Mammary Tumor Virus ; Beet Western Yellows Virus ; Simian Retrovirus type-1 ; Hepatitis Delta Virus ; translational frameshifting ; ribozyme ; nmr ; x-ray diffraction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recently, several high-resolution structures of RNA pseudoknots have become available. Here we review the progress in this area. The majority of the structures obtained belong to the classical or H-type pseudoknot family. The most complicated pseudoknot structure elucidated so far is the Hepatitis Delta Virus ribozyme, which forms a nested double pseudoknot. In particular, the structure-function relationships of the H-type pseudoknots involved in translational frameshifting have received much attention. All molecules considered show interesting new structural motifs. © 1999 John Wiley & Sons, Inc. Biopoly 48: 137-153, 1998
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    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 737-748 
    ISSN: 0887-624X
    Keywords: inverse microemulsion polymerization ; MADQUAT ; nucleation ; photopolymerization ; molecular weights ; flocculants ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of inverse microemulsions of 2-methacryloyl oxyethyl trimethyl ammonium chloride stabilized by a blend of nonionic emulsifiers (a sorbitan sesquioleate and a sorbitan monooleate) and initiated by UV light in the presence of Azobis(isobutyronitrile) (AIBN) was investigated. The effect of initiator concentration, light intensity, emulsifier concentration, and dispersed phase weight fraction on the polymerization rate (Rp), number of polymer particles (Np), and polymer molecular weight (Mw) was studied. The application of this process to tubular reactors is discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 737-748, 1998
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    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1217-1226 
    ISSN: 0887-624X
    Keywords: polypropylene ; pyrene ; two-solute system ; pulse radiolysis ; solute ionic species ; solute excited states ; low-temperature radiolysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A pulse radiolysis study of isotactic polypropylene (PP) film has been carried out with the main aims of investigating charge trapping in an undoped system and solute radical ion generation in an pyrene (Py) doped matrix. In PP, pulse radiolysis gives electron-positive hole pairs. The electron can be stabilized in the undoped system as a trapped electron, et-. The transient absorption spectrum of et- in the near-IR (up to 1800 nm) was observed in the temperature range 30-100 K. This IR absorption was not detected in the case of oxidized PP. In such a matrix electrons can be scavenged by oxidation products generating respective radical-anions (absorption in the UV RANGE, λ 〈 350 nm). In a doped matrix transient absorption bands centered at 450 and 500 nm were observed which can be assigned to the Py radical cation and anion, respectively. The recombination of these ionic species leads to monomer excited-state formation observed during and after the 17 ns pulse. Contrary to the Py-doped polyethylene no excimer emission was detected at room temperature even if Py content in PP was close to 0.02 mol dm-3. The rate of Py radical-ion decay was found to be temperature dependent. Two linear parts of the Arrhenius plot were observed which intersected at ca. 240 K, the glass transition temperature, Tg, for PP. The activation energies calculated for two parts of Arrhenius plot were equal to 111 and ca. 0.78 kJ mol-1 for T 〉 Tg and T 〈 Tg, respectively. Some preliminary results concerning the ionic processes in PP containing two solutes (Py, 3,3′-dimethyldiphenyl) were presented. The mechanism of ionic recombination in PP will be proposed and discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1217-1226, 1998
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    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1345-1348 
    ISSN: 0887-624X
    Keywords: acid functional ; telechelic ; benzyl alcohol ; poly(ε-caprolactone) ; polymerization ; living ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 883-888 
    ISSN: 0887-624X
    Keywords: temperature sensitive ; particle ; emulsion polymerization ; morphology ; adsorption ; enzyme ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two kinds of temperature-sensitive composite polymer particles were prepared by seeded emulsion copolymerizations of (dimethylamino)ethyl methacrylate and ethylene glycol dimethacrylate with 0.14 μm-sized polystyrene and 0.26 μm-sized poly(methylmethacrylate) seed particles. To evaluate the usefulness as a carrier for biomolecules, the enzymatic activities of trypsin adsorbed on these two composite polymer particles were measured at temperatures above and below each lower critical solution temperature (LCST). In both cases, adsorbed trypsin retained its enzymatic activity during repeated adsorption/desorption measurements. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 883-888, 1998
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  • 95
    ISSN: 0887-624X
    Keywords: (1→6)-2,5-anhydro-D-glucitol ; HPLC ; optical resolution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cyclopolymerization of 3,4-di-O-allyl-1,2 : 5,6-dianhydro-D-mannitol (1) was carried out using BF3·OEt2 and t-BuOK. The polymer obtained by the polymerization with BF3·OEt2 mainly consisted of (1→6)-bonded 3,4-di-O-allyl-2,5-anhydro-D-glucitol as the five-membered constitutional repeating unit, though it contained a small amount of other cyclic repeating units. On the other hand, during the polymerization using t-BuOK, the stereoregular polymer (1→6)-linked 3,4-di-O-allyl-2,5-anhydro-D-glucitol (2) was synthesized via a regio- and stereoselective mechanism. Cleavage of the allyl ether linkage in polymer 2 occurred to produce the polymer consisting of only 2,5-anhydro-D-glucitol units, i.e., (1→6)-2,5-anhydro-D-glucitol (3). Chromatographic enantioseparation of chloroquine and tröger base has been performed on (3,5-dimethylphenyl)carbamate and 4-methylbenzoate derivatives of 3 as a chiral stationary phase for high-performance liquid chromatography. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 901-909, 1998
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 939-947 
    ISSN: 0887-624X
    Keywords: fluorine ; perfluoropolyether ; polyester ; segmented ; thermoplastic ; interfacial synthesis ; thermal transitions ; dynamic-mechanical properties ; chemical resistance ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linear segmented polyesters containing soft perfluoropolyether (PFPE) and hard aromatic segments are obtained by an interfacial polycondensation reaction of an acyl chloride-ended fluorinated prepolymer with various aromatic diphenols in the presence of phase transfer catalysts (PTC) as accelerators. Experimental conditions for reaching high molecular weights are discussed. The calorimetric analysis (DSC) of all the polyesters synthesized shows a typical biphasic morphology, where a very low Tg (〈 -110°C) corresponding to the segregated PFPE moiety, is always accompanied by another Tg or a higher melting temperature, depending on the nature of the hard phase. Dynamic-mechanical analysis (DMA) has been carried out confirming the DSC results and suggesting diversified mechanical behaviors at the various temperatures in line with the amorphous or semicrystalline nature of the polymer. Chemical resistance was finally tested by dipping in several solvents and chemicals. The new polyesters show high contact angles, a moderate swelling in many organic solvents and excellent stability in aggressive hydrolytic environments. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 939-947, 1998
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  • 97
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1919-1928 
    ISSN: 0887-624X
    Keywords: emulsion polymerization ; vinylidene chloride ; kinetics ; sodium lauryl sulfate ; potassium persulfate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Emulsion polymerization of vinylidene chloride was carried out at 50°C using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator, respectively. Contrary to the results so far reported, the stirring rate did not affect the progress of the polymerization and such an abnormal kinetic behavior as the rate of polymerization suddenly drops in the course of polymerization was not observed. The number of polymer particles produced was proportional to the 0.7 power of the concentration of emulsifier forming micelles and to the 0.3 power of the initial initiator concentration, respectively, and was independent of the initial monomer concentration. The rate of polymerization was in proportion to the 0.3 power of the concentration of emulsifier forming micelles, to the 0.5 power of the initial initiator concentration, to the 0.2 power of the initial monomer concentration, and to the 0.45 power of the number of polymer particles, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1919-1928, 1998
    Additional Material: 13 Ill.
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  • 98
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1961-1964 
    ISSN: 0887-624X
    Keywords: Poly(4,4′-phenylene-3,3′,4,4′-biphenyltetracarboxyimide) ; poly(4,4′-oxydiphenylenepyromellitimide) ; precursor solution ; aprotic polar solvent ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 4 Ill.
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  • 99
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    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1969-1972 
    ISSN: 0887-624X
    Keywords: hydrosilation ; polymer ; siloxane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 2 Ill.
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  • 100
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1995-1999 
    ISSN: 0887-624X
    Keywords: poly-γ-D-glutamic acid ; biopolymer ; covalent modification ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methods for the covalent modification in aqueous solution of poly-γ-D-glutamic acid from Bacillus licheniformis have been studied. Co-derivatization of a synthetic UV-absorbent amine and ethanolamine, using a water-soluble carbodi-imide coupling agent, yielded a water-soluble modified polymer. Derivatization of the polymer was accompanied by cleavage of the γ-linked polypeptide backbone, and a reduction in molecular mass from 170 to 10 kDa. A procedure was developed for the removal of noncovalently bound ligands by treatment with 5 M CaCl2. The polymer sidechains also reacted in aqueous solution with p-nitrophenyl acetate to form covalent linkages. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 1995-1999, 1998
    Additional Material: 4 Ill.
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