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171.
Values of K, delta G(o), delta H(o), delta S(o) and delta C(po) for the binding reaction of small organic ligands forming 1:1 complexes with either alpha- or beta-cyclodextrin were obtained by titration calorimetry from 15 degrees C to 45 degrees C. A hydrogen bond or hydrophobic interaction was introduced by adding a single functional group to the ligand. The thermodynamics of binding with and without the added group are compared to estimate the contribution of the hydrogen bond or hydrophobic interaction. A change in the environment of a functional group is required to influence the binding thermodynamics, but molecular size-dependent solute-solvent interactions have no effect. For phenolic O-H-O hydrogen bond formation, delta H(o) varies from -2 to -1.4 kcal mol(-1) from 15 degrees C to 45 degrees C, and delta C(p) is increased by 18 cal K(-1) mol(-1). The hydrophobic interaction has an opposite effect: in alpha-cyclodextrin, delta C(po) = -13.3 cal K(-1) mol(-1) per ligand -CH(2)-, identical to values found for the transfer of a -CH(2)-group from water to a nonpolar environment. At room temperature, the hydrogen bond and the -CH(2)-interaction each contribute about -600 cal mol(-1) to the stability (delta G(o)) of the complex. With increased temperature, the hydrogen bond stability decreases (i.e., hydrogen bonds "melt"), but the stability of the hydrophobic interaction remains essentially constant. 相似文献
172.
Patricia Kramer Jennifer Yount Thomas Mitchell Dante LaMorticella Roque Carrero-Valenzuela Everett Lovrien Irene Maumenee Michael Litt 《Genomics》1996,35(3):539
Congenital cataracts are one of the most common major eye abnormalities and often lead to blindness in infants. At least a third of all cases are familial. Within this group, highly penetrant, autosomal dominant forms of congenital cataracts (ADCC) are most common. ADCC is a genetically heterogeneous group of disorders, in which at least eight different loci have been identified for nine clinically distinct forms. Among these, Armitageet al.(Nature Genet.9: 37–40, 1995) mapped a gene for cerulean blue cataracts to chromosome 17q24. Bodkeret al.(Am. J. Med. Genet.37: 54–59, 1990) described a large family with cerulean blue cataracts, in which the affected daughter of affected first cousins was presumed to be homozygous for the purported gene. We report linkage in this family to the region on chromosome 22q that includes two β crystallin genes (CRYBB2, CRYBB3) and one pseudogene (CRYBB2P1). The affected female in question is homozygous at all markers. 相似文献
173.
Separate polyclonal antibodies have previously been developed against the domoic-acid-producingPseudonitzschia multiseries (=Pseudo-nitzschia pungens f.multiseries) and the non-toxicP. pungens (=P. pungens f.pungens). These antibodies bind to the surface of the diatoms as shown by immunofluorescence studies. Here we examine the molecular nature of the antigens by Western blotting (electro-immunoblotting) analysis. The major antigens for both polyclonal antibodies migrated as high molecular-weight diffuse bands, mostly remaining in the stacking gel, using an SDS-PAGE system. The antibodies prepared againstP. multiseries strongly labelled the high molecular-weight antigens of allP. multiseries strains tested and showed little reactivity towardsP. pungens extracts on Western blots.P. pungens antibodies strongly labelled high molecular-weightP. pungens antigens and faintly labelled a fewP. multiseries antigens. The selectivity of the antibodies for their respective species correlates with the results of the immunofluorescence experiments, suggesting that the antigens examined in this study are responsible for the selective labelling in immunofluorescence studies. The electrophoretic mobility and the antibody labelling of antigens were not altered by proteolytic digestion of cell pellets. However, disruption of carbohydrates in the pellets by treatment with periodic acid resulted in loss of the antigen. These data suggest that the major antigens of toxicP. multiseries and non-toxicP. pungens are high molecular-weight (°>100kDa) polysaccharides located on the surface of these diatoms.Author for correspondence 相似文献
174.
An Ecosystem View of the Restoration of the Kissimmee River 总被引:1,自引:0,他引:1
Clifford N. Dahm Kenneth W. Cummins H. Maurice Valett Ross L. Coleman 《Restoration Ecology》1995,3(3):225-238
Restoration of the Kissimmee River and floodplain ultimately will involve restoring 70 km of river channel and riparian zone and 11,000 ha of wetland over a period of two decades. Restoring ecosystem integrity is a crucial goal of the project, and the evaluation program is designed to assess the success of this endeavor. Major components of the riverine and floodplain ecosystem will be evaluated, guided by conceptual models of their structure and function. These studies will be referenced to historic conditions of the past and to present-day conditions in the channelized system. Enhanced connectivity and interactions between the river and floodplain, the interplay of abiotic and biotic variables, and interactions between trophic levels will restructure the channelized river and the largely drained floodplain that now exist. The key to evaluating the success of this ambitious project will be selecting measurements of the structure and function of the river and floodplain ecosystems that are responsive to this large-scale manipulation. The timing and duration of floodplain inundation, improved dissolved oxygen conditions, germination and establishment of wetland vegetation, and enhancement and expansion of rheophilic benthic invertebrate populations are critical initial elements of restoration. Further expected outcomes are an increase in the primary productivity of the ecosystem, expansion of the fish community into the reopened channels and onto the reflooded floodplain, and improved visitation and use by waterbirds in the restored regions. We highlight predictions of some of these key linkages and primary structural and functional attributes of the restored river and floodplain that should be measured. 相似文献
175.
Theoretical Basis of Protocols for Seed Storage III. Optimum Moisture Contents for Pea Seeds Stored at Different Temperatures 总被引:6,自引:1,他引:5
In previous work, we demonstrated that there was an optimummoisture level for seed storage at a given temperature (Vertucciand Roos, 1990), and suggested, using thermodynamic considerations,that the optimum moisture content increased as the storage temperaturedecreased (Vertucci and Roos, 1993b). In this paper, we presentdata from a two year study of aging rates in pea (Pisum sativum)seeds supporting the hypothesis that the optimum moisture contentfor storage varies with temperature. Seed viability and vigourwere monitored during storage under dark or lighted conditionsat relative humidities between 1 and 90%, and temperatures between-5 and 65°C. The optimum moisture content varied from 0·015g H2O g-1 d.wt at 65°C to 0·101 g H2O g-1 d.wt at15°C under dark conditions and from 0·057 at 35°Cto 0·092 g H2O g-1 d.wt at -5°C under lighted conditions.Our results suggest that optimum moisture contents cannot beconsidered independently of temperature. This conclusion hasimportant implications for 'ultra-dry' and cryopreservationtechnologies.Copyright 1994, 1999 Academic Press Seed storage, seed aging, seed longevity, water content, temperature, glass, desiccation damage, ultradry, Pisum sativum L., pea, cryopreservation 相似文献
176.
177.
Locus Heterogeneity for Waardenburg Syndrome is Predictive of Clinical Subtypes 总被引:5,自引:4,他引:1 下载免费PDF全文
Lindsay A. Farrer Kathleen S. Arnos James H. Asher Clinton T. Baldwin Scott R. Diehl Thomas B. Friedman Jacquie Greenberg Kenneth M. Grundfast Christopher Hoth Anil K. Lalwani Barbara Landa Kate Leverton Aubrey Milunsky Robert Morell Walter E. Nance Valerie Newton Rajkumar Ramesar Valluri S. Rao Jennifer E. Reynolds Theresa B. San Agustin Edward R. Wilcox Ingrid Winship Andrew P. Read 《American journal of human genetics》1994,55(4):728-737
Waardenburg syndrome (WS) is a dominantly inherited and clinically variable syndrome of deafness, pigmentary changes, and distinctive facial features. Clinically, WS type I (WS1) is differentiated from WS type II (WS2) by the high frequency of dystopia canthorum in the family. In some families, WS is caused by mutations in the PAX3 gene on chromosome 2q. We have typed microsatellite markers within and flanking PAX3 in 41 WS1 kindreds and 26 WS2 kindreds in order to estimate the proportion of families with probable mutations in PAX3 and to study the relationship between phenotypic and genotypic heterogeneity. Evaluation of heterogeneity in location scores obtained by multilocus analysis indicated that WS is linked to PAX3 in 60% of all WS families and in 100% of WS1 families. None of the WS2 families were linked. In those families in which equivocal lod scores (between −2 and +1) were found, PAX3 mutations have been identified in 5 of the 15 WS1 families but in none of the 4 WS2 families. Although preliminary studies do not suggest any association between the phenotype and the molecular pathology in 20 families with known PAX3 mutations and in four patients with chromosomal abnormalities in the vicinity of PAX3, the presence of dystopia in multiple family members is a reliable indicator for identifying families likely to have a defect in PAX3. 相似文献
178.
Mismatch Repair Genes on Chromosomes 2p and 3p Account for a Major Share of Hereditary Nonpolyposis Colorectal Cancer Families Evaluable by Linkage 总被引:17,自引:1,他引:16 下载免费PDF全文
Minna Nystrm-Lahti Ramon Parsons Pertti Sistonen Lea Pylkknen Lauri A. Aaltonen Fredrick S. Leach Stanley R. Hamilton Patrice Watson Earlene Bronson Ramon Fusaro Jennifer Cavalieri Jane Lynch Stephen Lanspa Tom Smyrk Patrick Lynch Thomas Drouhard Kenneth W. Kinzler Bert Vogelstein Henry T. Lynch Albert de la Chapelle Pivi Peltomki 《American journal of human genetics》1994,55(4):659-665
Two susceptibility loci for hereditary nonpolyposis colo-rectal cancer (HNPCC) have been identified, and each contains a mismatch repair gene: MSH2 on chromosome 2p and MLH1 on chromosome 3p. We studied the involvement of these loci in 13 large HNPCC kindreds originating from three different continents. Six families showed close linkage to the 2p locus, and a heritable mutation of the MSH2 gene was subsequently found in four. The 2p-linked kindreds included a family characterized by the lack of extracolonic manifestations (Lynch I syndrome), as well as two families with cutaneous manifestations typical of the Muir-Torre syndrome. Four families showed evidence for linkage to the 3p locus, and a heritable mutation of the MLH1 gene was later detected in three. One 3p-linked kindred was of Amerindian origin. Of the remaining three families studied for linkage, one showed lod scores compatible with exclusion of both MSH2 and MLH1, while lod scores obtained in the other two families suggested exclusion of one HNPCC locus (MSH2 or MLH1) but were uninformative for markers flanking the other locus. Our results suggest that mismatch repair genes on 2p and 3p account for a major share of HNPCC in kindreds that can be evaluated by linkage analysis. 相似文献
179.
Use of an oriented transmembrane protein to probe the assembly of a supported phospholipid bilayer. 总被引:2,自引:1,他引:1 下载免费PDF全文
Planar-supported phospholipid bilayers formed by the adsorption of vesicles are increasingly used in the investigation of lipid-dependent reactions. We have studied the way in which these bilayers are formed with phospholipid vesicles containing the transmembrane protein Tissue Factor (TF). TF complexed with the serine protease, factor VIIa, is the primary initiator of blood coagulation by way of activation of the zymogen factor X. TF has been shown to orient randomly on the inner and outer leaflets of vesicles. We used proteolytic digestion to produce vesicles in which the extracellular domain of TF is located on the inner leaflet. These vesicles show no cofactor activity for factor VIIa as a result of the inability of the extracellular domain of TF to bind VIIa. After freeze/thawing, 50% of the cofactor activity was regained, indicating reorientation of the sequestered, inner leaflet TF. Adsorption of these vesicles to the inner surface of glass microcapillaries results in a continuous phospholipid bilayer. The microcapillaries were perfused with a solution of factors VIIa and X, and the effluent was monitored for factor Xa production, a sensitive measure of the activity of the TF-VIIa complex. For coatings produced with the digested vesicles, minimal TF-VIIa activity was observed, showing that the supported bilayer preserves the orientation of the leaflets in the vesicles, i.e., the outer leaflet of the vesicles forms the outer leaflet of the supported bilayer. 相似文献
180.
Neil J. Gemmell Axel Janke Patrick S. Western Jaclyn M. Watson Svante Pääbo Jennifer A. Marshall Graves 《Journal of molecular evolution》1994,39(2):200-205
The vertebrate mitochondrial genome is highly conserved in size and gene content. Among the chordates there appears to be one basic gene arrangement, but rearrangements in the mitochondrial gene order of the avian lineages have indicated that the mitochondrial genome may be more variable than once thought. Different gene orders in marsupials and eutherian mammals leave the ancestral mammalian order in some doubt. We have investigated the mitochondrial gene order in the platypus (Ornithorhynchus anatinus), a representative of the third major group of mammals, to determine which mitochondrial gene arrangement is ancestral in mammals. We have found that the platypus mtDNA conforms to the basic chordate gene arrangement, common to fish, amphibians, and eutherian mammals, indicating that this arrangement was the original mammalian arrangement, and that the unusual rearrangements observed in the avians and marsupials are probably lineage-specific.
Correspondence to: N.J. Gemmell 相似文献