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1.
Amino acid changes S180A (S-->A at site 180), H197Y, Y277F, T285A, and
A308S are known to shift the maximum wavelength of absorption (lambda max)
of red and green visual pigments toward blue, essentially in an additive
fashion. To test the generality of this "five-sites" rule, we have
determined the partial amino acid sequences of red and green pigments from
five mammalian orders (Artiodactyla, Carnivora, Lagomorpha, Perissodactyla,
and Rodentia). The result suggests that cat (Felis catus), dog (Canis
familiaris), and goat (Capra hircus) pigments all with AHYTA at the five
critical sites have lambda max values of approximately 530 nm, whereas rat
(Rattus norvegicus) pigment with AYYTS has a lambda max value of
approximately 510 nm, which is accurately predicted by the five-sites rule.
However, the observed lambda max values of the orthologous pigments of
European rabbit (Oryctolagus cuniculus), white-tailed deer (Odocoileus
virginianus), gray squirrel (Sciurus carolinensis), and guinea pig (Cavia
procellus) are consistently more than 10 nm higher than the predicted
values, suggesting the existence of additional molecular mechanisms for red
and green color vision. The inferred amino acid sequences of ancestral
organisms suggest that the extant mammalian red and green pigments appear
to have evolved from a single ancestral green-red hybrid pigment by
directed amino acid substitutions.
相似文献
2.
This study reports the sequence specific chemical shifts assignments for 76 residues of the 94 residues containing monomeric unit of the photosynthetic light-harvesting 2 transmembrane protein complex from Rhodopseudomonas acidophila strain 10050, using Magic Angle Spinning (MAS) NMR in combination with extensive and selective biosynthetic isotope labeling methods. The sequence specific chemical shifts assignment is an essential step for structure determination by MAS NMR. Assignments have been performed on the basis of 2-dimensional proton-driven spin diffusion 13C–13C correlation experiments with mixing times of 20 and 500 ms and band selective 13C–15N correlation spectroscopy on a series of site-specific biosynthetically labeled samples. The decreased line width and the reduced number of correlation signals of the selectively labeled samples with respect to the uniformly labeled samples enable to resolve the narrowly distributed correlation signals of the backbone carbons and nitrogens involved in the long -helical transmembrane segments. Inter-space correlations between nearby residues and between residues and the labeled BChl a cofactors, provided by the 13C–13C correlation experiments using a 500 ms spin diffusion period, are used to arrive at sequence specific chemical shift assignments for many residues in the protein complex. In this way it is demonstrated that MAS NMR methods combined with site-specific biosynthetic isotope labeling can be used for sequence specific assignment of the NMR response of transmembrane proteins. 相似文献
3.
Thiago?GazoniEmail author Simone?L?Gruber Ana?PZ?Silva Olivia?GS?Araújo Hideki?Narimatsu Christine?Strüssmann Célio?FB?Haddad Sanae?Kasahara 《BMC genetics》2012,13(1):109
Background
The karyotypes of Leptodactylus species usually consist of 22 bi-armed chromosomes, but morphological variations in some chromosomes and even differences in the 2n have been reported. To better understand the mechanisms responsible for these differences, eight species were analysed using classical and molecular cytogenetic techniques, including replication banding with BrdU incorporation.Results
Distinct chromosome numbers were found: 2n = 22 in Leptodactylus chaquensis, L. labyrinthicus, L. pentadactylus, L. petersii, L. podicipinus, and L. rhodomystax; 2n = 20 in Leptodactylus sp. (aff. podicipinus); and 2n = 24 in L. marmoratus. Among the species with 2n = 22, only three had the same basic karyotype. Leptodactylus pentadactylus presented multiple translocations, L. petersii displayed chromosome morphological discrepancy, and L. podicipinus had four pairs of telocentric chromosomes. Replication banding was crucial for characterising this variability and for explaining the reduced 2n in Leptodactylus sp. (aff. podicipinus). Leptodactylus marmoratus had few chromosomes with a similar banding patterns to the 2n = 22 karyotypes. The majority of the species presented a single NOR-bearing pair, which was confirmed using Ag-impregnation and FISH with an rDNA probe. In general, the NOR-bearing chromosomes corresponded to chromosome 8, but NORs were found on chromosome 3 or 4 in some species. Leptodactylus marmoratus had NORs on chromosome pairs 6 and 8. The data from C-banding, fluorochrome staining, and FISH using the telomeric probe helped in characterising the repetitive sequences. Even though hybridisation did occur on the chromosome ends, telomere-like repetitive sequences outside of the telomere region were identified. Metaphase I cells from L. pentadactylus confirmed its complex karyotype constitution because 12 chromosomes appeared as ring-shaped chain in addition to five bivalents.Conclusions
Species of Leptodactylus exhibited both major and minor karyotypic differences which were identified by classical and molecular cytogenetic techniques. Replication banding, which is a unique procedure that has been used to obtain longitudinal multiple band patterns in amphibian chromosomes, allowed us to outline the general mechanisms responsible for these karyotype differences. The findings also suggested that L. marmoratus, which was formerly included in the genus Adenomera, may have undergone great chromosomal repatterning.4.
Background
Routine antibiotic prophylaxis following snakebite is not recommended but evidence suggests that it may be common practice in Zimbabwe. This study set out to determine and describe the extent of this practice at Parirenyatwa Hospital, a large teaching hospital in Zimbabwe 相似文献5.
Inhibition of Sulfate Respiration by 1,8-Dihydroxyanthraquinone and Other Anthraquinone Derivatives 总被引:5,自引:1,他引:4
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FB I. Cooling C. L. Maloney E. Nagel J. Tabinowski J. M. Odom 《Applied microbiology》1996,62(8):2999-3004
Derivatives of 9,10-anthracenedione, or anthraquinone, were shown to inhibit respiratory sulfate reduction by pure cultures of sulfate-reducing bacteria, as well as by crude enrichment cultures. Structure-activity studies showed that an increasing degree of substitution of the anthraquinone nucleus resulted in increasing 50% inhibition (I(inf50)) values for sulfate respiration. Addition of charged ring substituents also resulted in an increase in the I(inf50) concentration. Experiments carried out with 1,8-dihydroxyanthraquinone demonstrated inhibition of hydrogen-dependent sulfate respiration but not hydrogen-dependent sulfite or thiosulfate respiration. Addition of pyruvate resulted in stimulation of sulfate-dependent hydrogen oxidation in the presence of the anthraquinone. These observations, together with a direct demonstration of uncoupling in French press vesicle preparations, suggest that the underlying mechanism of inhibition is uncoupling of ATP synthesis from electron transfer reactions. The low I(inf50) values for inhibition (0.5 to 10 (mu)M) and the relatively low general toxicity of anthraquinones suggest that these compounds may be useful for inhibition of sulfide generation in situations which are incompatible with the use of broadly toxic biocides. 相似文献
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8.
van Gammeren AJ Hulsbergen FB Hollander JG de Groot HJ 《Journal of biomolecular NMR》2004,30(3):267-274
Partly biosynthetic site-directed isotopically 13C enriched photosynthetic light-harvesting 2(LH2) complexes have been prepared from Rhodopseudomonas acidophila strain 10050 by using chemically labeled [1,2,3,4–13C], [1,4–13C] and [2,3–13C] succinic acid as a precursor in the growth medium. Two-dimensional proton driven spin diffusion (PDSD) solid state NMR correlation spectroscopy has been used to trace each individual 13C isotope from the labeled succinic acid precursor to its destination into the protein and into the embedded major light-absorbing bacteriochlorophyll cofactors. For both the residues of the protein and for the cofactors distinct labeling patterns have been deduced, for protein complexes prepared from [1,4–13C]-succinic acid or [2,3–13C]-succinic labeled media. All residues, except isoleucine and leucine, have been labeled almost homogeneously by the succinic acid precursor. Carbonyl carbons in the protein backbone were labeled by [1,4–13C]-succinic acid, while the C and C carbons of the residues were labeled by [2,3 13C]-succinic acid. Leucine and isoleucine residues were labeled using a uniformly labeled amino acid mixture in the medium. The pattern labeling yields an increase of the resolution and less spectral crowding. The partial labeling technique in combination with conventional solid state NMR methods at ultra high magnetic fields provides an attractive route to resolve chemical shifts for -helical transmembrane protein structures. 相似文献
9.
Prashant R Agrawal Mathias W Hofmann Nico J Meeuwenoord Dmitri V Filippov Holger Stalz Frans Hulsbergen Dieter Langosch Hermen S Overkleeft Huub De Groot 《Journal of peptide science》2007,13(2):75-80
The transmembrane segments of soluble N-ethylmaleimide-sensitive factor (SNARE) proteins or viral envelope proteins drive membrane fusion, which suggests that simple synthetic biology constructs for fusion exist and can be evaluated. We describe the high-yield synthesis of a set of de novo designed fusogenic peptides for use in functional investigations, which are highly enriched in 13C and 15N using three equivalents of labelled amino acids and optimized reaction conditions minimizing aggregation. The biomimetic peptides have a high purity >90% and show reproducible and fusogenic activity that correlates well with the intended functional design characteristics, from strongly fusogenic to almost non-fusogenic. 相似文献
10.
Adriaan?J.?van?Gammeren Frans?B.?Hulsbergen Cornelis?Erkelens Huub?J.?M.?de?GrootEmail author 《Journal of biological inorganic chemistry》2004,9(1):109-117
Mg(II)–porphyrin–ligand and (bacterio)chlorophyl–ligand coordination interactions have been studied by solution and solid-state MAS NMR spectroscopy. 1H, 13C and 15N coordination shifts due to ring currents, electronic perturbations and structural effects are resolved for imidazole (Im) and 1-methylimidazole (1-MeIm) coordinated axially to Mg(II)-OEP and (B)Chl a. As a consequence of a single axial coordination of Im or 1-MeIm to the Mg(II) ion, 0.9–5.2 ppm 1H, 0.2–5.5 ppm 13C and 2.1–27.2 ppm 15N coordination shifts were measured for selectively labeled [1,3-15N]-Im, [1,3-15N,2-13C]-Im and [1,3-15N,1,2-13C]-1-MeIm. The coordination shifts depend on the distance of the nuclei to the porphyrin plane and the perturbation of the electronic structure. The signal intensities in the 1H NMR spectrum reveal a five-coordinated complex, and the isotropic chemical shift analysis shows a close analogy with the electronic structure of the BChl a–histidine in natural light harvesting 2 complexes. The line broadening of the ligand responses support the complementary IR data and provide evidence for a dynamic coordination bond in the complex.Abbreviations (B)Chl a
(bacterio)chlorophyll a
- HMBC
heteronuclear multiple bond correlation
- Im
imidazole
- LH
light-harvesting
- 1-MeIm
1-methylimidazole
- Mg(II)-Por
Mg(II)-porphyrin macrocycle
- OEP
2,3,7,8,12,13,17,18-octaethylporphyrin 相似文献