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1.
Bodil Kjær Yean-Sung Jung Lian Yu John H. Golbeck Henrik Vibe Scheller 《Photosynthesis research》1994,41(1):105-114
The photosynthetic reaction center complex from the green sulfur bacteriumChlorobium vibrioforme has been isolated under anaerobic conditions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveals polypeptides with apparent molecular masses of 80, 40, 30, 18, 15, and 9 kDa. The 80- and 18-kDa polypeptides are identified as the reaction center polypeptide and the secondary donor cytochromec
551 encoded by thepscA andpscC genes, respectively. N-terminal amino acid sequences identify the 40-kDa polypeptide as the bacteriochlorophylla-protein of the baseplate (the Fenna-Matthews-Olson protein) and the 30-kDa polypeptide as the putative 2[4Fe-4S] protein encoded bypscB. Electron paramagnetic resonance (EPR) analysis shows the presence of an iron-sulfur cluster which is irreversibly photoreduced at 9K. Photoaccumulation at higher temperature shows the presence of an additional photoreduced cluster. The EPR spectra of the two iron-sulfur clusters resemble those of FA and FB of Photosystem I, but also show significantly differentg-values, lineshapes, and temperature and power dependencies. We suggest that the two centers are designated Center I (with calculatedg-values of 2.085, 1.898, 1.841), and Center II (with calculatedg-values of 2.083, 1.941, 1.878). The data suggest that Centers I and II are bound to thepscB polypeptide. 相似文献
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Evidence has been accumulating to support the process of reinforcement as a potential mechanism in speciation. In many species,
mate choice decisions are influenced by cultural factors, including learned mating preferences (sexual imprinting) or learned
mate attraction signals (e.g., bird song). It has been postulated that learning can have a strong impact on the likelihood
of speciation and perhaps on the process of reinforcement, but no models have explicitly considered learning in a reinforcement
context. We review the evidence that suggests that learning may be involved in speciation and reinforcement, and present a
model of reinforcement via learned preferences. We show that not only can reinforcement occur when preferences are learned
by imprinting, but that such preferences can maintain species differences easily in comparison with both autosomal and sex-linked
genetically inherited preferences. We highlight the need for more explicit study of the connection between the behavioral
process of learning and the evolutionary process of reinforcement in natural systems. 相似文献
6.
J M Gallo D Escalier P Grellier E Précigout M Albert G David J Schrével 《The journal of histochemistry and cytochemistry》1991,39(3):273-282
Among the monoclonal antibodies (MAb) selected after immunization of mice with a detergent-insoluble fraction from human spermatozoa, MAb 4D4 was found to stain in immunofluorescence the principal part of the acrosome of human spermatozoa. Acrosome reaction induced decreased and spotty 4D4 immunofluorescence staining. Immunoelectron microscopy before or after embedding revealed that the epitope defined by MAb 4D4 was sequestered in the anterior acrosomal matrix and, after the acrosome reaction, remained partly bound on matrix elements attached to the inner acrosomal membrane. Western blot analysis of sperm extracts showed that the epitope defined by MAb 4D4 was located on a 55 KD polypeptide in whole cells and on 55 and 50 KD polypeptides in non-ionic detergent fractions. Human proacrosin-enriched fraction obtained by FPLC purification exhibited several proteolytic activities against gelatin in gel enzymography: a 50 KD major band and two minor bands in the 20-30 KD area; the 50 KD polypeptide reacted with MAb 4D4 in Western blots. Furthermore, the 4D4-immunoprecipitated polypeptide from sperm extract showed that the 50 KD band exhibited proteolytic activity with an optimal pH at 8.0 that was strongly inhibited by soybean trypsin inhibitor and ZnCl2. MAb 4D4 also reacted with the acrosome of the monkey Macaca fascicularis but not with the acrosome of any of the other non-primate mammalian species examined so far. Various shape defects of the acrosomal principal region were revealed by 4D4 labeling of spermatozoa with head anomalies from infertile patients. MAb 4D4 also recognized proacrosin in paraffin-embedded human testis sections. These data make the monoclonal antiproacrosin antibody 4D4 an efficient tool for evaluation of the acrosomal status of human spermatozoa and spermatids. 相似文献
7.
S. Sæbøe-Larssen B. Urbanczyk Mohebi A. Lambertsson 《Molecular genetics and genomics : MGG》1997,255(2):141-151
The Minute phenotype results from mutations at?>50 loci scattered throughout the genome of Drosophila. Common traits of the Minute phenotype are short and thin bristles, slow development, and recessive lethality. Here, we report a novel P-element induced Minute mutation, P{lacW}M(3)66D 1 , that maps to region 66D on chromosome 3L. Flies heterozygous for P{lacW}M(3)66D 1 have a strong Minute phenotype. Molecular characterisation of the chromosomal region revealed three previously undescribed Drosophila genes clustered within a 5-kb genomic fragment. Two of the genes have significant sequence homology to genes for the mammalian ribosomal proteins L14 and RD, respectively, and share a joint 240-bp promoter region harbouring the P-element insert. Quantitative Northern blot analyses showed the mutation to affect RPL14 mRNA levels only. Interestingly, the reduction in abundance of RPL14 mRNA is not constitutive, indicating that the promoter function abolished by the inserted P-element is utilised with different efficiencies in different developmental situations. Remobilisation of the P element produced wild-type flies with normal levels of RPL14 mRNA, demonstrating that the mutant phenotype is caused by the insertion. P{lacW}M(3)66D 1 joins a growing list of Minute mutations associated with ribosomal protein-haploinsufficiency. 相似文献
8.
DNA typing of HLA-DR
β
chain genes can discriminate between undetected alleles and real homozygotes 总被引:1,自引:0,他引:1
The polymorphism of HLA-DR antigens has been studied by Southern blot hybridization under conditions specific for the detection of the DR
chain genes. Haplotype-specific patterns were defined with DNA from DR1, 2, 3, 4, 7, w8, w11, w12, and W13 homozygous typing cells, with restriction enzymes Eco RI, Bgl I, and Pvu II. Certain serological specificities, such as DR2, DR3, and DR7, can be encoded by distinct allelic forms of DR
chain genes. The procedure of DNA typing was applied to family analysis of individuals expressing only a single DR specificity upon serological typing. Three cases are described here: (1) in family GR, phenotypic DR 7 homozygotes correspond to genomic heterozygotes, and a novel DR7 allele is described: (2) in family RU, the genes corresponding to a serologically undetected (blank) DR allele were identified by restriction fragment length polymorphism (RFLP); this novel DR haplotype has an RFLP pattern similar to those of the DRw52 family, even though this specificity was not expressed on the DR-blank lymphocytes; (3) in family RG, there is no blank allele, but a homozygote RFLP situation at the DR subregion. 相似文献
9.
Quantitative electroelution of oligonucleotides and large DNA fragments from gels and purification by electrodialysis 总被引:5,自引:0,他引:5
We have designed a new device [Biotrap (Elutrap in the U.S.A. and Canada), available from Schleicher & Schuell] for electroelution, -concentration , and -dialysis of DNA and other charged macromolecules above 5 kDa. In an electric field, the DNA migrates in an open channel out of the gel slice through a microporous membrane, BT2, into the trap section, where it is retained by a very dense, non-adsorbant, and inert membrane BT1. Specifically designed for use in an electric field, the matrix of this new membrane is much denser than that of dialysis membranes. In contrast to dialysis membranes, BT1 will not adsorb large DNA fragments nor allow passage of small DNA fragments when subjected to an electric field. In the absence of an electric field, BT1 and BT2 effectively seal the trap, maintaining the final elution volume of the purified sample. The trap can contain from 200-600 microliter and is collected from above with a pipet. In the experiments described here, 85-95% of oligonucleotides (14-mer) and large (150 kb) DNA fragments were recovered, independent of fragment length. The purity of the eluted DNA was demonstrated by restriction enzyme digestion, nick-translation, primer extension, end-labeling with polynucleotide kinase, and ligation. Electrodialysis was successfully used for the complete removal of common contaminants inhibiting the polynucleotide kinase reaction and for the removal of CsCl from DNA samples. 相似文献
10.
Polarized resonance Raman spectra of chlorophyll (Chl) b oriented in a mixture of p-methoxybenzylideno-p'-butylaniline (MBBA) and p-ethoxybenzylideno-p'-butylaniline (EBBA) have been measured. The spectra have been analyzed and the second- and fourth-rank order parameters and the orientational distribution function of Chl b are presented. 相似文献