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41.
42.
Jacques Bernillon Marie-Louise Bouillant Jean-Louis Pittet Jean Favre-Bonvin Noël Arpin 《Phytochemistry》1984,23(5):1083-1087
The structure of mycosporine glutamine, a new compound, has been established and its presence demonstrated in two fungi Pyronema omphalodes and Glomerella cingulata. Mycosporine glutamic acid has been isolated from Helvella leucomelaneae. Co-occurrence of normycosporine glutamine, mycosporine glutamine and glucosylmycosporine glutaminol has been demonstrated in the fungus P. omphalodes. A biosynthetic pathway is proposed. Mycosporines have been compared by HPLC. 相似文献
43.
M.L. Bouillant F.Ferreres de Arce J. Favre-Bonvin J. Chopin A. Zoll G. Mathieu 《Phytochemistry》1984,23(11):2653-2657
Permethylated 6-C-diglycosyl-8-C-glycosylflavones and 6-C-glycosyl-8-C-diglycosylflavones gave well defined EIMS including the molecular peak and a fragmentation pattern characteristic of the 6-C-glycosyl residue. X″′-O-glycosides (8-C-disaccharides) are thus easily distinguished from X″-O-glycosides (6-C-disaccharides) and, in the latter, the position of the O-glycosidic bond should be deduced from the MS, after acid hydrolysis. Three new C-glycosylflavones have been characterized in this way from Spergularia rubra and Stellaria holostea. 相似文献
44.
The early adaptive evolution of calmodulin 总被引:7,自引:0,他引:7
Baba ML; Goodman M; Berger-Cohn J; Demaille JG; Matsuda G 《Molecular biology and evolution》1984,1(6):442-455
Interaction between gene duplication and natural selection in molecular
evolution was investigated utilizing a phylogenetic tree constructed by the
parsimony procedure from amino acid sequences of 50 calmodulin- family
protein members. The 50 sequences, belonging to seven protein lineages
related by gene duplication (calmodulin itself, troponin-C, alkali and
regulatory light chains of myosin, parvalbumin, intestinal calcium-binding
protein, and glial S-100 phenylalanine-rich protein), came from a wide
range of eukaryotic taxa and yielded a denser tree (more branch points
within each lineage) than in earlier studies. Evidence obtained from the
reconstructed pattern of base substitutions and deletions in these
ancestral loci suggests that, during the early history of the family,
selection acted as a transforming force on expressed genes among the
duplicates to encode molecular sites with new or modified functions. In
later stages of descent, however, selection was a conserving force that
preserved the structures of many coadapted functional sites. Each branch of
the family was found to have a unique average tempo of evolutionary change,
apparently regulated through functional constraints. Proteins whose
functions dictate multiple interaction with several other macromolecules
evolved more slowly than those which display fewer protein-protein and
protein-ion interactions, e.g., calmodulin and next troponin-C evolved at
the slowest average rates, whereas parvalbumin evolved at the fastest. The
history of all lineages, however, appears to be characterized by rapid
rates of evolutionary change in earlier periods, followed by slower rates
in more recent periods. A particularly sharp contrast between such fast and
slow rates is found in the evolution of calmodulin, whose rate of change in
earlier eukaryotes was manyfold faster than the average rate over the past
1 billion years. In fact, the amino acid replacements in the nascent
calmodulin lineage occurred at residue positions that in extant metazoans
are largely invariable, lending further support to the Darwinian hypothesis
that natural selection is both a creative and a conserving force in
molecular evolution.
相似文献
45.
The restriction enzyme TaqI digests 0.2% of the genomic DNA from the
grasshopper Caledia captiva to a family of sequences 168 bp in length
(length of consensus sequence). The sequence variation of this "Taq family"
of repeat units was examined among four races from C. captiva to assay the
pattern of evolution within this highly repeated DNA. The Taq-family
repeats are located in C-banded heterochromatin on at least one member of
each homologous pair of chromosomes; the locations range from centromeric
to telomeric. Thirty-nine cloned repeats isolated from two population 1A
individuals along with 11 clones from seven populations taken from three of
the races demonstrated sequence variation at 72 positions. Pairwise
comparisons of the cloned repeats, both within an individual and between
different races, indicate that levels of intraspecific divergence, as
measured by reproductive incompatibility, do not correlate with sequence
divergence among the 168-bp repeats. A number of subsequences within the
repeat remain unchanged among all 50 clones; the longest of these is 18 bp.
That the same 18-bp subsequence is present in all clones examined is a
finding that departs significantly (P less than 0.01) from what would be
expected to occur at random. Two other cloned repeats, from a
reproductively isolated race of C. captiva, have sequences that show 56%
identity with this 18-bp conserved region. An analysis showed that the
frequency of occurrence of an RsaI recognition site within the 168- bp
repeat in the entire Taq family agreed with that found in the cloned
sequences. These data, along with a partial sequence for the entire Taq
family obtained by sequencing uncloned repeats, suggest that the consensus
sequence from the cloned copies is representative of this highly repeated
family and is not a biased sample resulting from the cloning procedure. The
18-bp conserved sequence is part of a 42-bp sequence that possesses dyad
symmetry typical of protein-binding sites. We speculate that this may be
significant in the evolution of the Taq family of sequences.
相似文献
46.
H?Bukulmez AL?Matthews CM?Sullivan C?Chen MJ?Kraay RC?Elston RW?Moskowitz VM?Goldberg ML?WarmanEmail author 《Arthritis research & therapy》2005,8(1):R25
In order to determine whether there is a genetic component to hip or knee joint failure due to idiopathic osteoarthritis (OA),
we invited patients (probands) undergoing hip or knee arthroplasty for management of idiopathic OA to provide detailed family
histories regarding the prevalence of idiopathic OA requiring joint replacement in their siblings. We also invited their spouses
to provide detailed family histories about their siblings to serve as a control group. In the probands, we confirmed the diagnosis
of idiopathic OA using American College of Rheumatology criteria. The cohorts included the siblings of 635 probands undergoing
total hip replacement, the siblings of 486 probands undergoing total knee replacement, and the siblings of 787 spouses. We
compared the prevalence of arthroplasty for idiopathic OA among the siblings of the probands with that among the siblings
of the spouses, and we used logistic regression to identify independent risk factors for hip and knee arthroplasty in the
siblings. Familial aggregation for hip arthroplasty, but not for knee arthroplasty, was observed after controlling for age
and sex, suggesting a genetic contribution to end-stage hip OA but not to end-stage knee OA. We conclude that attempts to
identify genes that predispose to idiopathic OA resulting in joint failure are more likely to be successful in patients with
hip OA than in those with knee OA. 相似文献
47.
48.
49.
Marie Louise Bouillant André Besset Jean Favre-Bonvin Jean Chopin 《Phytochemistry》1979,18(4):690-691
2″,3″,4″ and 6″-O-glycosides of 6-C-glucosylflavones can be differentiated by the MS of the hydrolysis products of their permethyl ethers. 相似文献
50.
Intercalation of proflavine and a platinum derivative of proflavine into double-helical Poly(A) 下载免费PDF全文
The equilibria and kinetics of the interactions of proflavine (PR) and its platinum-containing derivative [PtCl(tmen)(2)HNC(13)H(7)(NHCH(2)CH(2))(2)](+) (PRPt) with double-stranded poly(A) have been investigated by spectrophotometry and Joule temperature-jump relaxation at ionic strength 0.1 M, 25 degrees C, and pH 5.2. Spectrophotometric measurements indicate that base-dye interactions are prevailing. T-jump experiments with polarized light showed that effects due to field-induced alignment could be neglected. Both of the investigated systems display two relaxation effects. The kinetic features of the reaction are discussed in terms of a two-step series mechanism in which a precursor complex DS(I) is formed in the fast step, which is then converted to a final complex in the slow step. The rate constants of the fast step are k(1) = (2.5 +/- 0.4) x 10(6) M(-1) s(-1), k(-1) = (2.4 +/- 0.1) x 10(3) s(-1) for poly(A)-PR and k(1) = (2.3 +/- 0.1) x 10(6) M(-1) s(-1), k(-1) = (1.6 +/- 0.2) x 10(3) s(-1) for poly(A)-PRPt. The rate constants for the slow step are k(2) = (4.5 +/- 0.5) x 10(2) s(-1), k(-2) = (1.7 +/- 0.1) x 10(2) s(-1) for poly(A)-PR and k(2) = 9.7 +/- 1.2 s(-1), k(-2) = 10.6 +/- 0.2 s(-1) for poly(A)-PRPt. Spectrophotometric measurements yield for the equilibrium constants and site size the values K = (4.5 +/- 0.1) x 10(3) M(-1), n = 1.3 +/- 0.5 for poly(A)-PR and K = (2.9 +/- 0.1) x 10(3) M(-1), n = 2.3 +/- 0.6 for poly(A)-PRPt. The values of k(1) are similar and lower than expected for diffusion-limited reactions. The values of k(-1) are similar as well. It is suggested that the formation of DS(I) involves only the proflavine residues in both systems. In contrast, the values of k(2) and k(-2) in poly(A)-PRPt are much lower than in poly(A)-PR. The results suggest that in the complex DS(II) of poly(A)-PRPt both proflavine and platinum residues are intercalated. In addition, a very slow process was detected and ascribed to the covalent binding of Pt(II) to the adenine. 相似文献