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  • 1
    Publication Date: 1998-05-23
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Agosto, M -- Allan, J -- Benson, C -- Berger, E A -- Blumenthal, R -- Burton, D -- Clements, J -- Coffin, J -- Connor, R -- Cullen, B -- Desrosiers, R -- Dimitrov, D -- Doms, R -- Emerman, M -- Feinberg, M -- Fultz, P -- Gerard, C -- Gonsalves, G -- Haase, A -- Haigwood, N -- Hirsch, V -- Ho, D -- Hoxie, J A -- Hu, S L -- Zingale, D -- New York, N.Y. -- Science. 1998 May 8;280(5365):803, 804-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9599148" target="_blank"〉PubMed〈/a〉
    Keywords: *AIDS Vaccines/immunology ; Acquired Immunodeficiency Syndrome/prevention & control ; *Clinical Trials as Topic ; HIV Envelope Protein gp120/immunology ; HIV-1/immunology ; Humans ; National Institutes of Health (U.S.) ; United States
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 1999-03-19
    Description: Structural maturation of fiber tracts in the human brain, including an increase in the diameter and myelination of axons, may play a role in cognitive development during childhood and adolescence. A computational analysis of structural magnetic resonance images obtained in 111 children and adolescents revealed age-related increases in white matter density in fiber tracts constituting putative corticospinal and frontotemporal pathways. The maturation of the corticospinal tract was bilateral, whereas that of the frontotemporal pathway was found predominantly in the left (speech-dominant) hemisphere. These findings provide evidence for a gradual maturation, during late childhood and adolescence, of fiber pathways presumably supporting motor and speech functions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Paus, T -- Zijdenbos, A -- Worsley, K -- Collins, D L -- Blumenthal, J -- Giedd, J N -- Rapoport, J L -- Evans, A C -- New York, N.Y. -- Science. 1999 Mar 19;283(5409):1908-11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Quebec H3A 2B4, Canada. tomas@bic.mni.mcgill.ca〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10082463" target="_blank"〉PubMed〈/a〉
    Keywords: Adolescent ; *Aging ; Axons/physiology/ultrastructure ; Brain/anatomy & histology/*growth & development ; Brain Mapping ; Child ; Child, Preschool ; Female ; Frontal Lobe/anatomy & histology/growth & development ; Humans ; Magnetic Resonance Imaging ; Male ; Motor Skills ; Myelin Sheath/ultrastructure ; Nerve Fibers/ultrastructure ; Neural Conduction ; Neural Pathways/anatomy & histology/*growth & development ; Regression Analysis ; Speech ; Spinal Cord/anatomy & histology ; Synaptic Transmission ; Temporal Lobe/anatomy & histology/growth & development
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 1991-09-20
    Description: A human intestinal intraepithelial lymphocyte (IEL) T cell line was established from jejunum to characterize the structure and function of the alpha beta T cell antigen receptors (TCRs) expressed by this population. Single-sided polymerase chain reaction (PCR) amplification cloning and quantitative PCR amplification of the TCR chains from the cell line and from fresh IELs demonstrated that IELs were oligoclonal. The IEL T cell line exhibited CD1-specific cytotoxicity and a dominant IEL T cell clone was CD1c-specific. Thus, human jejunal intraepithelial lymphocytes are oligoclonal and recognize members of the CD1 gene family.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Balk, S P -- Ebert, E C -- Blumenthal, R L -- McDermott, F V -- Wucherpfennig, K W -- Landau, S B -- Blumberg, R S -- 5 KO8 DK01886/DK/NIDDK NIH HHS/ -- CA-01310/CA/NCI NIH HHS/ -- DK42166/DK/NIDDK NIH HHS/ -- New York, N.Y. -- Science. 1991 Sep 20;253(5026):1411-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Hematology-Oncology Division, Beth Israel Hospital, Harvard Medical School, Boston, MA 02215.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1716785" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Antigens, CD/*genetics/immunology ; Antigens, CD1 ; Base Sequence ; Cell Line ; Clone Cells ; Epithelium/physiology ; Humans ; Jejunum/immunology ; Molecular Sequence Data ; Oligonucleotide Probes ; Polymerase Chain Reaction/methods ; Receptors, Antigen, T-Cell/*genetics ; T-Lymphocytes/*immunology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 2008-09-06
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rowley, Janet D -- Blumenthal, Thomas -- New York, N.Y. -- Science. 2008 Sep 5;321(5894):1302-4. doi: 10.1126/science.1163791.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medicine, University of Chicago, 5841 South Maryland Avenue, MC 2115, Chicago, IL 60637, USA. jrowley@medicine.bsd.uchicago.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18772424" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Line ; Chromosomes, Human, Pair 17/genetics ; Chromosomes, Human, Pair 7/genetics ; Endometrial Neoplasms/genetics ; Endometrium/cytology/*metabolism ; Female ; Gene Fusion ; Gene Rearrangement ; Humans ; Macaca mulatta ; Menstrual Cycle ; Neoplasm Proteins/*genetics ; RNA, Guide/genetics ; RNA, Messenger/*genetics ; *Trans-Splicing ; Transcription Factors/*genetics ; *Translocation, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2013-05-21
    Description: 〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3772710/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3772710/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McGuire, Amy L -- Joffe, Steven -- Koenig, Barbara A -- Biesecker, Barbara B -- McCullough, Laurence B -- Blumenthal-Barby, Jennifer S -- Caulfield, Timothy -- Terry, Sharon F -- Green, Robert C -- CA154517/CA/NCI NIH HHS/ -- HG003178/HG/NHGRI NIH HHS/ -- HG005092/HG/NHGRI NIH HHS/ -- HG006485/HG/NHGRI NIH HHS/ -- HG006492/HG/NHGRI NIH HHS/ -- HG006500/HG/NHGRI NIH HHS/ -- HG006612-02/HG/NHGRI NIH HHS/ -- HG006615/HG/NHGRI NIH HHS/ -- HG02213/HG/NHGRI NIH HHS/ -- P20 HG007243/HG/NHGRI NIH HHS/ -- R01 CA154517/CA/NCI NIH HHS/ -- R01 HG002213/HG/NHGRI NIH HHS/ -- R01 HG003178/HG/NHGRI NIH HHS/ -- R01 HG005092/HG/NHGRI NIH HHS/ -- R01-CA154517/CA/NCI NIH HHS/ -- U01 HG006485/HG/NHGRI NIH HHS/ -- U01 HG006492/HG/NHGRI NIH HHS/ -- U01 HG006500/HG/NHGRI NIH HHS/ -- Intramural NIH HHS/ -- New York, N.Y. -- Science. 2013 May 31;340(6136):1047-8. doi: 10.1126/science.1240156. Epub 2013 May 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Medical Ethics and Health Policy, Baylor College of Medicine, Houston, TX 77030, USA. amcguire@bcm.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23686340" target="_blank"〉PubMed〈/a〉
    Keywords: Adult ; Child ; Disease/*genetics ; *Genetic Predisposition to Disease ; Genetic Testing/ethics/standards ; Genome-Wide Association Study/ethics/standards ; Genomics/*ethics/*standards ; Humans ; *Incidental Findings ; Laboratories/ethics/standards/statistics & numerical data ; Mutation/ethics ; Neoplasms/genetics ; *Practice Guidelines as Topic ; Sequence Analysis, DNA/ethics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2003-03-01
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bass, Gary D -- Blumenthal, Paul D -- Corfman, Phil -- Darney, Philip D -- Gonsalves, Gregg -- Levin, Arthur A -- Trussell, James -- Shields, Wayne C -- New York, N.Y. -- Science. 2003 Feb 28;299(5611):1313.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12610277" target="_blank"〉PubMed〈/a〉
    Keywords: Acquired Immunodeficiency Syndrome/prevention & control ; *Advisory Committees ; Federal Government ; Humans ; *Politics ; *Public Health ; *Science ; United States
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Publication Date: 2014-03-29
    Description: Regulated transcription controls the diversity, developmental pathways and spatial organization of the hundreds of cell types that make up a mammal. Using single-molecule cDNA sequencing, we mapped transcription start sites (TSSs) and their usage in human and mouse primary cells, cell lines and tissues to produce a comprehensive overview of mammalian gene expression across the human body. We find that few genes are truly 'housekeeping', whereas many mammalian promoters are composite entities composed of several closely separated TSSs, with independent cell-type-specific expression profiles. TSSs specific to different cell types evolve at different rates, whereas promoters of broadly expressed genes are the most conserved. Promoter-based expression analysis reveals key transcription factors defining cell states and links them to binding-site motifs. The functions of identified novel transcripts can be predicted by coexpression and sample ontology enrichment analyses. The functional annotation of the mammalian genome 5 (FANTOM5) project provides comprehensive expression profiles and functional annotation of mammalian cell-type-specific transcriptomes with wide applications in biomedical research.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4529748/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4529748/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉FANTOM Consortium and the RIKEN PMI and CLST (DGT) -- Forrest, Alistair R R -- Kawaji, Hideya -- Rehli, Michael -- Baillie, J Kenneth -- de Hoon, Michiel J L -- Haberle, Vanja -- Lassmann, Timo -- Kulakovskiy, Ivan V -- Lizio, Marina -- Itoh, Masayoshi -- Andersson, Robin -- Mungall, Christopher J -- Meehan, Terrence F -- Schmeier, Sebastian -- Bertin, Nicolas -- Jorgensen, Mette -- Dimont, Emmanuel -- Arner, Erik -- Schmidl, Christian -- Schaefer, Ulf -- Medvedeva, Yulia A -- Plessy, Charles -- Vitezic, Morana -- Severin, Jessica -- Semple, Colin A -- Ishizu, Yuri -- Young, Robert S -- Francescatto, Margherita -- Alam, Intikhab -- Albanese, Davide -- Altschuler, Gabriel M -- Arakawa, Takahiro -- Archer, John A C -- Arner, Peter -- Babina, Magda -- Rennie, Sarah -- Balwierz, Piotr J -- Beckhouse, Anthony G -- Pradhan-Bhatt, Swati -- Blake, Judith A -- Blumenthal, Antje -- Bodega, Beatrice -- Bonetti, Alessandro -- Briggs, James -- Brombacher, Frank -- Burroughs, A Maxwell -- Califano, Andrea -- Cannistraci, Carlo V -- Carbajo, Daniel -- Chen, Yun -- Chierici, Marco -- Ciani, Yari -- Clevers, Hans C -- Dalla, Emiliano -- Davis, Carrie A -- Detmar, Michael -- Diehl, Alexander D -- Dohi, Taeko -- Drablos, Finn -- Edge, Albert S B -- Edinger, Matthias -- Ekwall, Karl -- Endoh, Mitsuhiro -- Enomoto, Hideki -- Fagiolini, Michela -- Fairbairn, Lynsey -- Fang, Hai -- Farach-Carson, Mary C -- Faulkner, Geoffrey J -- Favorov, Alexander V -- Fisher, Malcolm E -- Frith, Martin C -- Fujita, Rie -- Fukuda, Shiro -- Furlanello, Cesare -- Furino, Masaaki -- Furusawa, Jun-ichi -- Geijtenbeek, Teunis B -- Gibson, Andrew P -- Gingeras, Thomas -- Goldowitz, Daniel -- Gough, Julian -- Guhl, Sven -- Guler, Reto -- Gustincich, Stefano -- Ha, Thomas J -- Hamaguchi, Masahide -- Hara, Mitsuko -- Harbers, Matthias -- Harshbarger, Jayson -- Hasegawa, Akira -- Hasegawa, Yuki -- Hashimoto, Takehiro -- Herlyn, Meenhard -- Hitchens, Kelly J -- Ho Sui, Shannan J -- Hofmann, Oliver M -- Hoof, Ilka -- Hori, Furni -- Huminiecki, Lukasz -- Iida, Kei -- Ikawa, Tomokatsu -- Jankovic, Boris R -- Jia, Hui -- Joshi, Anagha -- Jurman, Giuseppe -- Kaczkowski, Bogumil -- Kai, Chieko -- Kaida, Kaoru -- Kaiho, Ai -- Kajiyama, Kazuhiro -- Kanamori-Katayama, Mutsumi -- Kasianov, Artem S -- Kasukawa, Takeya -- Katayama, Shintaro -- Kato, Sachi -- Kawaguchi, Shuji -- Kawamoto, Hiroshi -- Kawamura, Yuki I -- Kawashima, Tsugumi -- Kempfle, Judith S -- Kenna, Tony J -- Kere, Juha -- Khachigian, Levon M -- Kitamura, Toshio -- Klinken, S Peter -- Knox, Alan J -- Kojima, Miki -- Kojima, Soichi -- Kondo, Naoto -- Koseki, Haruhiko -- Koyasu, Shigeo -- Krampitz, Sarah -- Kubosaki, Atsutaka -- Kwon, Andrew T -- Laros, Jeroen F J -- Lee, Weonju -- Lennartsson, Andreas -- Li, Kang -- Lilje, Berit -- Lipovich, Leonard -- Mackay-Sim, Alan -- Manabe, Ri-ichiroh -- Mar, Jessica C -- Marchand, Benoit -- Mathelier, Anthony -- Mejhert, Niklas -- Meynert, Alison -- Mizuno, Yosuke -- de Lima Morais, David A -- Morikawa, Hiromasa -- Morimoto, Mitsuru -- Moro, Kazuyo -- Motakis, Efthymios -- Motohashi, Hozumi -- Mummery, Christine L -- Murata, Mitsuyoshi -- Nagao-Sato, Sayaka -- Nakachi, Yutaka -- Nakahara, Fumio -- Nakamura, Toshiyuki -- Nakamura, Yukio -- Nakazato, Kenichi -- van Nimwegen, Erik -- Ninomiya, Noriko -- Nishiyori, Hiromi -- Noma, Shohei -- Noazaki, Tadasuke -- Ogishima, Soichi -- Ohkura, Naganari -- Ohimiya, Hiroko -- Ohno, Hiroshi -- Ohshima, Mitsuhiro -- Okada-Hatakeyama, Mariko -- Okazaki, Yasushi -- Orlando, Valerio -- Ovchinnikov, Dmitry A -- Pain, Arnab -- Passier, Robert -- Patrikakis, Margaret -- Persson, Helena -- Piazza, Silvano -- Prendergast, James G D -- Rackham, Owen J L -- Ramilowski, Jordan A -- Rashid, Mamoon -- Ravasi, Timothy -- Rizzu, Patrizia -- Roncador, Marco -- Roy, Sugata -- Rye, Morten B -- Saijyo, Eri -- Sajantila, Antti -- Saka, Akiko -- Sakaguchi, Shimon -- Sakai, Mizuho -- Sato, Hiroki -- Savvi, Suzana -- Saxena, Alka -- Schneider, Claudio -- Schultes, Erik A -- Schulze-Tanzil, Gundula G -- Schwegmann, Anita -- Sengstag, Thierry -- Sheng, Guojun -- Shimoji, Hisashi -- Shimoni, Yishai -- Shin, Jay W -- Simon, Christophe -- Sugiyama, Daisuke -- Sugiyama, Takaai -- Suzuki, Masanori -- Suzuki, Naoko -- Swoboda, Rolf K -- 't Hoen, Peter A C -- Tagami, Michihira -- Takahashi, Naoko -- Takai, Jun -- Tanaka, Hiroshi -- Tatsukawa, Hideki -- Tatum, Zuotian -- Thompson, Mark -- Toyodo, Hiroo -- Toyoda, Tetsuro -- Valen, Elvind -- van de Wetering, Marc -- van den Berg, Linda M -- Verado, Roberto -- Vijayan, Dipti -- Vorontsov, Ilya E -- Wasserman, Wyeth W -- Watanabe, Shoko -- Wells, Christine A -- Winteringham, Louise N -- Wolvetang, Ernst -- Wood, Emily J -- Yamaguchi, Yoko -- Yamamoto, Masayuki -- Yoneda, Misako -- Yonekura, Yohei -- Yoshida, Shigehiro -- Zabierowski, Susan E -- Zhang, Peter G -- Zhao, Xiaobei -- Zucchelli, Silvia -- Summers, Kim M -- Suzuki, Harukazu -- Daub, Carsten O -- Kawai, Jun -- Heutink, Peter -- Hide, Winston -- Freeman, Tom C -- Lenhard, Boris -- Bajic, Vladimir B -- Taylor, Martin S -- Makeev, Vsevolod J -- Sandelin, Albin -- Hume, David A -- Carninci, Piero -- Hayashizaki, Yoshihide -- BB/F003722/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/G022771/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/I001107/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- MC_PC_U127597124/Medical Research Council/United Kingdom -- MC_UP_1102/1/Medical Research Council/United Kingdom -- R01 DE022969/DE/NIDCR NIH HHS/ -- R01 GM084875/GM/NIGMS NIH HHS/ -- England -- Nature. 2014 Mar 27;507(7493):462-70. doi: 10.1038/nature13182.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24670764" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Atlases as Topic ; Cell Line ; Cells, Cultured ; Cluster Analysis ; Conserved Sequence/genetics ; Gene Expression Regulation/genetics ; Gene Regulatory Networks/genetics ; Genes, Essential/genetics ; Genome/genetics ; Humans ; Mice ; *Molecular Sequence Annotation ; Open Reading Frames/genetics ; Organ Specificity ; Promoter Regions, Genetic/*genetics ; RNA, Messenger/analysis/genetics ; Transcription Factors/metabolism ; Transcription Initiation Site ; Transcription, Genetic/genetics ; Transcriptome/*genetics
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 111-117 
    ISSN: 1432-0827
    Keywords: Calcium-deficient hydroxyapatite ; Amorphous calcium phosphate ; Bone ; Radial distribution function ; Carbonate apatite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary When amorphous calcium phosphate (ACP) was transformed to crystalline hydroxyapatite (HA) in a series of aqueous slurry concentrations ranging from low to high, the higher slurry concentrations produced more Ca-deficient HA as measured by Ca/P ratio and heat-produced pyrophosphate. We feel that the excess solution phosphate produced in the higher slurry transformations results in lower Ca/P ratio HA. It has been suggested that an ACP is the precursor to bone apatite. Regulation of the in vivo ACP slurry concentration could then control the stoichiometry and, therefore, the metabolic activity of bone apatite. X-ray radial distribution function (RDF) analyses showed that CO 3 2− substitution in HA creates far greater structural distortions than do Ca deficiencies. The latter, however, do produce small, but observable, structural distortions when compared to stoichiometric HA. It now seems clear that the RDF of bone apatite can be modeled by a synthetic, Ca-deficient, CO 3 2− -containing HA.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 13 (1973), S. 235-243 
    ISSN: 1432-0827
    Keywords: Hydroxyapatite ; Bone ; Amorphous ; Calcium ; Phosphate ; Hydrogen Bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé De l'hydroxyapatite (HA) est préparé en mélangeant du phosphate de calcium amorphe (ACP), contenant du Cl comme oligo-élément, dans de l'eau distillée tamponnée à pH 7,4 par du Tris-HCl à 25, 37, 60, 80 et 100°. Un tel Ha contient moins de 1% (25°) à11% (100°) de Cl initialement contenu dans le précurseur ACP. Ces résultats suggèrent que le mécanisme principal de conservion consiste en une série de processus contrôlés par des vitesses de solubilité, permettant aux ions de s'échapper des ACP en voie de disolution avant le début de la nucléation de l'HA.In situ, le réarrangement de l'ACP n'explique pas la fuite ionique et ne semble pas responsable de la conversion. Le spectre infra-rouge de surface hautement spécifique d'HA, préparé à 25° et 37°, ne montre pas d'élongation OH ou des bandes OH équilibrées, alors que la surface spécifique inférieure de l'HA (60°, 80°, 100°) présente des bandes nettes de ces modes vibrationnels. Cet effet est atrribué à une liaison hydrogène de groupement OH structural à la surface de cristaux d'HA, présentant une monocouche d'eau fortement adsorbée à la surface de l'HA. Comme dans les autres systèmes, la formation de liaison hydrogene élimine probablement les bandes d'absorption OH, de telle sorte que seuls les groupements OH, situés à l'intérieur des cristaux, donnent des bandes OH nettes, non perturbées. Au fur et à mesure que la surface spécifique de l'HA diminue, l'effet d'élimination s'atténue par suite d'une décroissance concomittante du pourcentage de groupements OH superficiels. Ainsi peut s'expliquer l'absence de modes vibrationnels OH dans le spectre infra-rouge du minéral osseux, étant donné que l'apatite osseux a une surface spécifique identique à celle de l'HA synthétisé à 25° et 37°.
    Abstract: Zusammenfassung Hydroxyapatit (HA) wurde hergestellt, indem amorphes Calciumphosphat (ACP), welches eingeschlossenes Cl als ein Tracer-Ion enthielt, in destilliertem Wasser, mit Tris-HCl auf pH 7,4 gepuffert, bei 25, 37, 60, 80 und 100° gerührt wurde. So hergestelltes HA enthielt bei 25° weniger als 1%, bei 100° 11% der Cl-Menge, welche ursprünglich im ACP eingeschlossen war. Diese Ergebnisse deuten darauf hin, daß der Hauptmechanismus der Umwandlung eine Reihe von durch die Lösung hervorgerufenen Veränderungen ist, welche es den Ionen ermöglichen, aus dem sich auflösenden ACP auszutreten, bevor die HA-Nukleation einsetzt. In situ ist der Ionenaustritt aus dem umgebildeten ACP nicht möglich und ist wahrscheinlich bei der Umwandlung nicht beteiligt. Die Infrarotspektren von hochspezifischem Oberflächen-HA, welches bei 25° und 37° hergestellt worden war, zeigten keine OH-Dehnungs- oder Schwankungsstreifen, während weniger spezifisches Oberflächen-HA (60°, 80°, 100°) Scharfe Streifen von diesen Vibrationsarten zeigt. Diese Wirkung wird der Tatsache zugeschrieben, daß strukturelle OH-Gruppen auf der Oberfläche der HA-Kristalle mit der dort vorhandenen stark adsorbierten Wassermonolayer eine Wassersotffbindung eingehen. Wie in anderen Systemen verwischt die Wasserstoffbindung wahrscheinlich die OH-Absorptionsstreifen, so daß nur die OH-Gruppen im Inneren der Kristalle scharfe, unveränderte OH-Streifen liefern. Je mehr die spezifische Oberfläche des HA abnimmt, desto kleiner wird die verwischende Wirkung, denn der Prozentsatz der an der Oberfläche liegenden OH-Gruppen nimmt ebenfalls ab. Dies erklärt eventuell die beobachtete Abwesenheit von OH-Vibrationsarten im Infrarotspektrum von Knochenmineral, da Knochenapatit eine spezifische Oberfläche hat, die mit derjenigen von HA verglichen werden kann, welches bei 25° und 37° synthetisiert wurde.
    Notes: Abstract Hydroxyapatite (HA) was prepared by stirring amorphous calcium phosphate (ACP), which contained occluded Cl− as a tracer ion, in distilled water buffered to pH 7.4 by tris-HCl at 25, 37, 60, 80 and 100°. HA made in this manner contained from less than 1% (25°) to 11% (100°) of the amount originally occluded in the precursor ACP. These results suggest that the principal mechanism of conversion is a series of solution- mediated rate processes that enable ions to move away from the dissolving ACP before the onset of HA nucleation.In situ ACP rearrangement does not provide for ion escape and is probably not involved in the conversion. The infrared spectra of high specific surface HA prepared at 25° and 37° showed no OH stretching or OH librational bands, while the lower specific surface HA (60°, 80°, 100°) displayed sharp bands of these vibrational modes. This effect is attributed to hydrogen bonding of structural OH groups on the surface on HA crystals with the strongly adsorbed water monolayer present on HA. As in other systems, hydrogen bond formation probably smears out the OH absorption bands so that only OH groups in the crystal interior yield sharp, unperturbed OH bands. As the HA specific surface decreases, the smearing effect becomes minimal due to a concomitant decrease in the percentage of surface-located OH groups. This may explain the observed absence of OH vibrational modes in the infrared spectrum of bone mineral, since bone apatite has a specific surface comparable to that of HA synthesized at 25° and 37°.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 36 (1984), S. 439-441 
    ISSN: 1432-0827
    Keywords: Osteomalacia ; Aluminum ; Hydroxyapatite ; Mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
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