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81.
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Efficiency and selectivity of 30 and 150 kd inorganic ultrafiltration membranes (Techsep) toward tuna hemoglobin and myoglobin were studied. The influence of pH and ionic strength was investigated. Mass flow of myoglobin was higher at its isoelectric pH (8.6) and for low ionic strength (1.5 mM). This result was related to the absence of electrostatic repulsion between myoglobin and the surface of the dynamic membrane. The use of high ionic strength 0.15 M NaCl involved an apparent dimerisation of myoglobin and consequently a lower permeation through the membrane due to the molecular weight increase. The permeation and retention of hemoglobin did not agree with the effect of pH observed with myoglobin (best permeation at isoelectric pH) but followed the behavior of myoglobin. This was explained by a myoglobin concentration 10 times higher than hemoglobin concentration. The yield of retention selectivity was investigated. Selectivity of the membrane at pH 8.6 and 1.5 mM was favorable to myoglobin (increase of 40%) whereas a reversed selectivity was observed at pH 7.3, 0.15 M. (c) 1996 John Wiley & Sons, Inc. 相似文献
84.
Multivariate analysis of human immunodeficiency virus type 1 neutralization data. 总被引:6,自引:6,他引:0 下载免费PDF全文
P N Nyambi J Nkengasong P Lewi K Andries W Janssens K Fransen L Heyndrickx P Piot G van der Groen 《Journal of virology》1996,70(9):6235-6243
We report on the use of spectral map analysis of the inter- and intraclade neutralization data of 14 sera of human immunodeficiency virus type 1 (HIV-1)-infected individuals and 16 primary isolates, representing genetic clades A to H in group M and group O. This multivariate analysis has been used previously to study the interaction between drugs and receptors and between viruses and antiviral compounds. The analysis reveals the existence of neutralization clusters, not correlated with the known genetic clades. The structural factors that have been identified may correlate with the most important neutralization epitopes. Three key primary HIV-1 isolates, which allow discrimination of sera that are likely or unlikely to neutralize primary isolates from most of the genetic clades, were identified. Our method of analysis will facilitate the evaluation as well as the design of suitable HIV-1 vaccines, which induce high-titer interclade cross-neutralizing antibodies. 相似文献
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Caccone A; Moriyama EN; Gleason JM; Nigro L; Powell JR 《Molecular biology and evolution》1996,13(9):1224-1232
Drosophila melanogaster belongs to a closely related group of eight species
collectively known as the melanogaster subgroup; all are native to
sub-Saharan Africa and islands off the east coast of Africa. The
phylogenetic relationships of most species in this subgroup have been well
documented; however, the three most closely related species, D. simulans,
D. sechellia, and D. mauritiana, have remained problematic from a
phylogenetic standpoint as no data set has unambiguously resolved them. We
present new DNA sequence data on the nullo and Serendipity-alpha genes and
combine them with all available nuclear DNA sequence data; the total data
encompass 12 genes and the ITS of rDNA. A methodological problem arose
because nine of the genes had information on intraspecific polymorphisms in
at least one species. We explored the effect of inclusion/exclusion of
polymorphic sites and found that it had very little effect on phylogenetic
inferences, due largely to the fact that 82% of polymorphisms are
autapomorphies (unique to one species). We have also reanalyzed our
previous DNA-DNA hybridization data with a bootstrap procedure. The
combined sequence data set and the DNA-DNA hybridization data strongly
support the sister status of the two island species, D. sechellia and D.
mauritiana. This at least partially resolves what had been a paradox of
parallel evolution in these two species.
相似文献
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88.
INTRoDUCTIoNlYho1iumrePensL,whiteclover,isaneconomicallyimportantplantspeciesintemperatepastures.Asbrieflyreportedby[1],ithas16pairsofchromosomes(2n=32).Asyet,nodetailedcytologicalexaminationofthisspecies,suchasC-banding,hasbeenrep0rted.Inthelastdecade,thetechnique0fC-bandinghasbeenusedt0examinehighlyrepeatedsequencesinplantchrom0s0mesandhasprovidedausefultoolf0rtheanalysis0fcyt0geneticstructureincr0pplants[2-71.Inplants,thechr0m0s0mall0calizationofhighlyrepeatedDNAsequencesbyinsituhybr… 相似文献
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The period (per) locus has received much attention in molecular evolution
studies because it is one of the best studied "behavioral genes" and
because it offers insight into the evolution of repetitive sequences. We
studied most of the coding region of per in Drosophila willistoni and
confirmed previously observed patterns of conservation and divergence among
distantly related species. Five regions are so highly diverged that they
cannot be aligned, whereas a region encompassing the PAS domain is very
conserved. Structural and nucleotide polymorphism patterns in the
willistoni group are not the same as those observed in previously studied
species. We sequenced the region homologous to the highly polymorphic
threonine-glycine repeat of D. melanogaster in multiple strains of D.
willistoni, as well as in other members of willistoni group, and found an
unusual amount of conservation in this region. However, the next
nonconserved region downstream in the sequence is quite variable and
polymorphic for the number of repeated glycines. The glycine codon usage is
significantly different in this glycine repeat as compared to other parts
of the gene. We were able to plot the directionality of change in the
glycine repeat region onto a phylogeny and find that the addition of
glycines is the general trend with the diversification of the willistoni
group.
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