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  • 1
    Electronic Resource
    Electronic Resource
    Characteristics of permeation and separation of dimethyl acrylamidemethyl methacrylate random and graft copolymer membranes for a benzene/cyclohexane mixture (1997)
    Springer
    Polymer bulletin 39 (1997), S. 733-740 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. When a benzene/cyclohexane mixture was permeated through poly(dimethyl acrylamide-random-methyl methacrylate) (DMAA-r-MMA) and poly(dimethyl acrylamide)-graft-poly(methyl methacrylate) (DMAA-g-MMA) membranes by pervaporation, the benzene-permselectivity of the DMAA-r-MMA membrane changed from the diffusivity selectivity to the solubility selectivity with increasing DMAA content but DMAA-g-MMA membranes with a high DMAA content had the higher apparent diffusivity selectivity than the apparent solubility selectivity. Furthermore, the apparent solubility selectivity for a benzene/cyclohexane mixture between the DMAA-r-MMA membrane and the DMAA-g-MMA membrane with a high DMAA content was remarkably different. These results were attributed to the difference of structure between the copolymers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050210
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  • 2
    Electronic Resource
    Electronic Resource
    Permeation and separation characteristics for benzene/cyclohexane mixtures through tosylcellulose membranes in pervaporation (1999)
    Springer
    Cellulose 6 (1999), S. 221-231 
    Details
    ISSN: 1572-882X
    Keywords: benzene/cyclohexane mixture ; benzene‐permselectivity ; degree of tosylation ; mechanism of separation ; tosylcellulose membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Tosylcelluloses (TosCells) with different degrees of tosylation were synthesized as membrane materials for the separation of benzene/cyclohexane (Bz/Chx) mixtures. TosCell membranes showed a high benzene‐permselectivity for the Bz/Chx mixtures in pervaporation (PV). An increase in the benzene concentration in the feed mixtures increased permeation rate but decreased the benzene‐permselectivity of the TosCell membranes. The increase in the permeation rate was attributed to the increase of the degree of swelling of the TosCell membranes by the feed mixtures and the decrease in the benzene‐permselectivity was mainly caused by the decrease of sorption selectivity. With low benzene concentrations in the Bz/Chx mixtures, the permeation rate of a TosCell membrane with a higher degree of tosylation was greater than that with a lower degree of tosylation, but was vice versa with a high benzene concentration. The benzene‐permselectivity of the former TosCell membrane was higher than that of the latter membrane. Differences of the permeation rate and benzene‐permselectivity with changes in the benzene concentration in the feed mixture and degree of tosylation of the TosCell membrane were significantly influenced by the degree of swelling of the TosCell membrane and the benzene concentration sorbed into the TosCell membrane. Mechanism of separation for the Bz/Chx mixtures through the TosCell membranes is discussed by the solution–diffusion model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009296930025
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  • 3
    Electronic Resource
    Electronic Resource
    Protein Tyrosine Kinase cDNAs from Amphioxus, Hagfish, and Lamprey: Isoform Duplications Around the Divergence of Cyclostomes and Gnathostomes (1999)
    Springer
    Journal of molecular evolution 49 (1999), S. 601-608 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Protein tyrosine kinases — isoforms — hagfish — lamprey — amphioxus — gene duplication — phylogenetic tree — evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Animals evolved a variety of gene families involved in cell–cell communication and developmental control by gene duplication and domain shuffling. Each family is made up of several subtypes or subfamilies with distinct structures and functions, which diverged by gene duplications and domain shufflings before the divergence of parazoans and eumetazoans. Since the separation from protostomes, vertebrates expanded the multiplicity of members (isoforms) in the same subfamily by further gene duplications in their early evolution before the fish–tetrapod split. To know the dates of isoform duplications more closely, we have conducted isolation and sequencing cDNAs encoding the fibroblast growth factor receptor, Eph, src, and platelet-derived growth factor receptor subtypes belonging to the protein tyrosine kinase family from Branchiostoma belcheri, an amphioxus, Eptatretus burgeri, a hagfish, and Lampetra reissneri, a lamprey. From a phylogenetic tree of each subfamily inferred from a maximum likelihood (ML) method, together with a bootstrap analysis based on the ML method, we have shown that the isoform duplications frequently occurred in the early evolution of vertebrates around or just before the divergence of cyclostomes and gnathostomes by gene duplications and possibly chromosomal duplications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006581
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  • 4
    Electronic Resource
    Electronic Resource
    Monophyly of Lampreys and Hagfishes Supported by Nuclear DNA–Coded Genes (1999)
    Springer
    Journal of molecular evolution 49 (1999), S. 729-735 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Cyclostomes — Gnathostomes — Glycolytic enzymes — Calreticulin — RNA polymerases — Molecular phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The phylogenetic position of hagfishes in vertebrate evolution is currently controversial. The 18S and 28S rRNA trees support the monophyly of hagfishes and lampreys. In contrast, the mitochondrial DNAs suggest the close association of lampreys and gnathostomes. To clarify this controversial issue, we have conducted cloning and sequencing of the four nuclear DNA–coded single-copy genes encoding the triose phosphate isomerase, calreticulin, and the largest subunit of RNA polymerase II and III. Based on these proteins, together with the Mn superoxide dismutase for which hagfish and lamprey sequences are available in database, phylogenetic trees have been inferred by the maximum likelihood (ML) method of protein phylogeny. It was shown that all the five proteins prefer the monophyletic tree of cyclostomes, and the total log-likelihood of the five proteins significantly supports the cyclostome monophyly at the level of ±1 SE. The ML trees of aldolase family comprising three nonallelic isoforms and the complement component group comprising C3, C4, and C5, both of which diverged during vertebrate evolution by gene duplications, also suggest the cyclostome monophyly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006595
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  • 5
    Electronic Resource
    Electronic Resource
    An Estimate of Divergence Time of Parazoa and Eumetazoa and That of Cephalochordata and Vertebrata by Aldolase and Triose Phosphate Isomerase Clocks (1997)
    Springer
    Journal of molecular evolution 45 (1997), S. 97 -106 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Divergence time — Molecular clock — Aldolase — Triose phosphate isomerase — Sponge — Amphioxus — Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Previously we suggested that four proteins including aldolase and triose phosphate isomerase (TPI) evolved with approximately constant rates over long periods covering the whole animal phyla. The constant rates of aldolase and TPI evolution were reexamined based on three different models for estimating evolutionary distances. It was shown that the evolutionary rates remain essentially unchanged in comparisons not only between different classes of vertebrates but also between vertebrates and arthropods and even between animals and plants, irrespective of the models used. Thus these enzymes might be useful molecular clocks for inferring divergence times of animal phyla. To know the divergence time of Parazoa and Eumetazoa and that of Cephalochordata and Vertebrata, the aldolase cDNAs from Ephydatia fluviatilis, a freshwater sponge, and the TPI cDNAs from Ephydatia fluviatilis and Branchiostoma belcheri, an amphioxus, have been cloned and sequenced. Comparisons of the deduced amino acid sequences of aldolase and TPI from the freshwater sponge with known sequences revealed that the Parazoa–Eumetazoa split occurred about 940 million years ago (Ma) as determined by the average of two proteins and three models. Similarly, the aldolase and TPI clocks suggest that vertebrates and amphioxus last shared a common ancestor around 700 Ma and they possibly diverged shortly after the divergence of deuterostomes and protostomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006208
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  • 6
    Electronic Resource
    Electronic Resource
    Protein Tyrosine Phosphatases from Amphioxus, Hagfish, and Ray: Divergence of Tissue-Specific Isoform Genes in the Early Evolution of Vertebrates (2000)
    Springer
    Journal of molecular evolution 50 (2000), S. 302-311 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Protein tyrosine phosphatase — Amphioxus — Hagfish — Ray — Tissue-specific isoform — Gene duplication — Phylogenetic tree — Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Since separation from fungi and plants, multicellular animals evolved a variety of gene families involved in cell–cell communication from a limited number of ancestral precursors by gene duplications in two separate periods of animal evolution. In the very early evolution of animals before the separation of parazoans and eumetazoans, animals underwent extensive gene duplications by which different subtypes (subfamilies) with distinct functions diverged. The multiplicity of members (isoforms) in the same subtype increased by further gene duplications (isoform duplications) in the first half of chordate evolution before the fish–tetrapod split; different isoforms are virtually identical in structure and function but differ in tissue distribution. From cloning and phylogenetic analyses of four subfamilies of the protein tyrosine kinase (PTK) family, we recently showed extensive isoform duplications in a limited period around or just before the cyclostome–gnathostome split. To obtain a reliable estimate for the divergence time of vertebrate isoforms, we have conducted isolation of cDNAs encoding the protein tyrosine phosphatases (PTPs) from Branchiostoma belcheri, an amphioxus, Eptatretus burgeri, a hagfish, and Potamotrygon motoro, a ray. We obtained 33 different cDNAs in total, most of which belong to known PTP subfamilies. The phylogenetic analyses of five subfamilies based on the maximum likelihood method revealed frequent isoform duplications in a period around or just before the gnathostome–cyclostome split. An evolutionary implication was discussed in relation to the Cambrian explosion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002399910035
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  • 7
    Electronic Resource
    Electronic Resource
    Multiple Protein Tyrosine Phosphatases in Sponges and Explosive Gene Duplication in the Early Evolution of Animals Before the Parazoan–Eumetazoan Split (1999)
    Springer
    Journal of molecular evolution 48 (1999), S. 654-662 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Protein tyrosine phosphatase — Classification — Sponge — Gene duplication — Phylogenetic tree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Protein tyrosine phosphatases (PTPs) regulate various physiological events in animal cells. They comprise a diverse family which are classified into two categories, receptor type and nonreceptor type. From the domain organization and phylogenetic tree, we have classified known PTPs into 17 subtypes (9 receptor-type and 8 nonreceptor-type PTPs) which are characterized by different organization of functional domain and independent cluster in tree. The receptor type PTPs are thought to be implicated in cell–cell adhesion by association of cell adhesion molecules. Since sponges are the most primitive multicellular animals and are thought to be lacking cell cohesiveness and coordination typical of eumetazoans, cloning and sequencing of PTP cDNAs of Ephydatia fluviatilis (freshwater sponge) have been conducted by RT-PCR to determine whether or not sponges have PTP genes in their genomes. We have isolated nine PTPs, of which five are possibly receptor type. A phylogenetic tree including the sponge PTPs revealed that most of the gene duplications that gave rise to the 17 subtypes had been completed in the very early evolution of animals before the parazoan–eumetazoan split, the earliest branching among extant animal phyla. The family tree also revealed the rapid evolutionary rate of PTP subtypes in the early stage of animal evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006509
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular evolution of mRNA: A method for estimating evolutionary rates of synonymous and amino acid substitutions from homologous nucleotide sequences and its application (1980)
    Springer
    Journal of molecular evolution 16 (1980), S. 23-36 
    Details
    ISSN: 1432-1432
    Keywords: Amino acid difference ; Synonymous difference ; Selective constraint ; mRNA evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A method for estimating the evolutionary rates of synonymous and amino acid substitutions from homologous nucleotide sequences is presented. This method is applied to genes of øX174 and G4 genomes, histone genes andβ-globin genes, for which homologous nucleotide sequences are available for comparison to be made. It is shown that the rates of synonymous substitutions are quite uniform among the non-overlapping genes of øX174 and G4 and among histone genes H4, H2B, H3 and H2A. A comparison between øX174 and G4 reveals that, in the overlapping segments of the A-gene, the rate of synonymous substitution is reduced more significantly than the rate of amino acid substitution relative to the corresponding rate in the nonoverlapping segment. It is also suggested that, in the coding regions surrounding the splicing points of intervening sequences ofβ-globin genes, there exist rigid secondary structures. It is in only these regions that theβ-globin genes show the slowing down of evolutionary rates of both synonymous and amino acid substitutions in the primate line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01732067
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  • 9
    Electronic Resource
    Electronic Resource
    Maximum likelihood inference of protein phylogeny and the origin of chloroplasts (1990)
    Springer
    Journal of molecular evolution 31 (1990), S. 151-160 
    Details
    ISSN: 1432-1432
    Keywords: Evolutionary tree ; Amino acid sequence ; Insertion/deletion ; Bootstrap probability ; psbA ; Prochlorothrix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A maximum likelihood method for inferring protein phylogeny was developed. It is based on a Markov model that takes into account the unequal transition probabilities among pairs of amino acids and does not assume constancy of rate among different lineages. Therefore, this method is expected to be powerful in inferring phylogeny among distantly related proteins, either orthologous or parallogous, where the evolutionary rate may deviate from constancy. Not only amino acid substitutions but also insertion/deletion events during evolution were incorporated into the Markov model. A simple method for estimating a bootstrap probability for the maximum likelihood tree among alternatives without performing a maximum likelihood estimation for each resampled data set was developed. These methods were applied to amino acid sequence data of a photosynthetic membrane protein,psbA, from photosystem II, and the phylogeny of this protein was discussed in relation to the origin of chloroplasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02109483
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular clock of silent substitution: At least six-fold preponderance of silent changes in mitochondrial genes over those in nuclear genes (1982)
    Springer
    Journal of molecular evolution 19 (1982), S. 28-35 
    Details
    ISSN: 1432-1432
    Keywords: Synonymous substitution ; Uniform Rate of Evolution ; Rapid Evolution of mtDNA ; Ck Gene of b4 Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary For each of eleven different types of nuclear genes, comparisons of the protein coding sequences were made between human, mouse and rat pairwisely, and the evolutionary rate of silent substitution, v S nucl. , was estimated. It is shown that the v S nucl. is not only very high (=5.37×10−9/site/yr), but also approximately uniform for different genes regardless of the types, which confirms our previous results (Miyata et al. 1980b). This is in sharp contrast to the rate of protein evolution which differes greatly from protein to protein. Furthermore the v S nucl. is shown to be approximately constant with respect to different divergence times, at least within a short time period (≤75 Myr). Based on these observations, we propose a new molecular clock which has several advantages over a protein clock. Using this clock, we show that the rate of amino acid replacement in the immunoglobulin Ck gene of b4 rabbit is unexpectedly high, almost comparable to the rate of silent changes. This rate may be the highest one for protein evolution that we know so far. We further examine the rate of silent substitutions in mitochondrial genes comparing mouse and rat. Surprisingly the rate is extremely high (≥35×10−9/site/yr), at least 6-times as high as the corresponding rate of nuclear genes. Based on the estimate, we discuss a possible origin of the rapid rate found in mitochondrial DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02100221
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