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1.
Glycosyl composition and linkage analysis of cell wall polysaccharides were examined in apical root zones excised from water-stressed and unstressed wheat seedlings (Triticum durum Desf.) cv. Capeiti ("drought-tolerant") and cv. Creso ("drought sensitive"). Wall polysaccharides were sequentially solubilized to obtain three fractions: CDTA+Na(2)CO(3) extract, KOH extract and the insoluble residue (alpha-cellulose). A comparison between the two genotypes showed only small variations in the percentages of matrix polysaccharides (CDTA+Na(2)CO(3) plus KOH extract) and of the insoluble residues (alpha-cellulose) in water-stressed and unstressed conditions. Xylosyl, glucosyl and arabinosyl residues represented more than 90mol% of the matrix polysaccharides. The linkage analysis of matrix polysaccharides showed high levels of xyloglucans (23-39mol%), and arabinoxylans (38-48mol%) and a low amount of pectins and (1-->3), (1-->4)-beta-d-glucans. The high level of xyloglucans was supported by the release of the diagnostic disaccharide isoprimeverose after Driselase digestion of KOH-extracted polysaccharides. In the "drought-tolerant" cv. Capeiti the mol% of side chains of rhamnogalacturonan I and II significantly increased in response to water stress, whereas in cv. Creso, this increase did not occur. The results support a role of the pectic side chains during water stress response in a drought-tolerant wheat cultivar.  相似文献   

2.
Ralstonia eutropha NCIMB 11599 and ATCC 17699 were grown, and their productions of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] compared. In flask cultures ofR. eutropha NCIMB 11599, cell concentration, P(3HB-co-4HB) concentration and polymer content decreased considerably with increases in the γ-butyrolactone concentration, and the 4HB fraction was also very low (maximum 1.74 mol%). In fed-batch cultures ofR. eutropha NCIMB 11599, glucose and γ-butyrolactone were fed as the carbon sources, under a phosphate limitation strategy. When glucose was fed as the sole carbon source, with its concentration controlled using an on-line glucose analyzer, 86% of the P(3HB) homopolymer was obtained from 201 g/L of cells. In a two-stage fed-batch culture, where the cell concentration was increased to 104 g/L, with glucose fed in the first step and constant feeding of γ-butyrolactone, at 6 g/h, in the second, final cell concentration at 67 h was 106 g/L, with a polymer content of 82%, while the 4HB fraction was only 0.7 mol%. When the same feeding strategy was applied to the fedbatch culture ofR. eutropha ATCC 17699, where the cell concentration was increased to 42 g/L, by feeding fructose in the first step and γ-butyrolactone (1.5 g/h) in the second, the final cell concentration, polymer content and 4HB fraction at 74 h were 51 g/L, 35% and 32 mol%, respectively. In summary,R. eutropha ATCC 17699 was better thanR. eutropha NCIMB 11599 in terms of P(3HB-co-4HB) production with various 4HB fractions.  相似文献   

3.
Subcellular fractionation of rat sciatic nerve was developed to determine the specific localization of gangliosides in the nerve membrane fractions. Myelin, microsomal, and a plasma membrane-like fraction were isolated and purified by sucrose density gradient centrifugation. These subfractions were characterized by electron microscopy, marker enzyme assays, and their protein and lipid profile. In rat sciatic nerve myelin, 90 mol% of the total gangliosides were monosialogangliosides. LM1 (sialosyl-lactoneotetraosylceramide) (61 mol%) and GM3 (21%) were the major gangliosides of the rat nerve myelin. Two other neolacto series of gangliosides, viz., sialosyl-lactoneonorhexaosylceramide and sialosyl-lactoneooctaosylceramide, were also localized mostly in the myelin fraction. GM1 was only a minor (less than 2%) ganglioside in myelin. The ganglioside patterns of the microsomal and plasma membrane-like fractions were similar with minor quantitative differences and were entirely different from that of myelin. Monosialogangliosides were approximately 70-75 mol% of the total in these fractions. The major gangliosides of the microsomal and plasma membrane-like fractions were GM3 (approximately 40%) and GM1 (approximately 20%). LM1 in these fractions was minimal (less than approximately 5%). Significant amounts of GM3 with N-glycolylneuraminic acid (approximately 10%) and GM1b (4-14%) were also identified in the microsomal and plasma membrane-like fractions but not in myelin. These and the higher lactoneo series of gangliosides have not been previously reported to be present in the rat nervous system. Almost exclusive localization of LM1 in myelin in rat peripheral nervous system is consistent with our previous observation that deposition of LM1 in the nerve with age was very similar to that of myelin marker lipids cerebrosides and sulfatides.  相似文献   

4.
The plant gum isolated from sap of the lac tree, Rhus vernicifera (China), was separated into two fractions having mol. wt. 84,000 and 27,700 by aqueous-phase gel-permeation chromatography. The fractions contain d-galactose (65 mol%), 4-O-methyl-d-glucuronic acid (24 mol%), d-glucuronic acid (3 mol%), l-arabinose (4 mol%), and l-rhamnose (3 mol%). Smith degradation of the carboxyl-reduced polysaccharides gives products of halved molecular weight, and these consist of a β-(1→3)-linked galactopyranan main chain and side chains made up of galactopyranose residues. Peripheral groups, such as α-d-Galp-, α-d-Galp-(1→6)-β-d-Galp-, 4-O-methyl-β-d-GlcpA-, and 4-O-methyl-β-d-GlcpA-(1→6)-β-d-Galp-, are attached to this interior core through β-(1→3)- or β-(1→6)-linkages.  相似文献   

5.
A neuronal nuclear fraction (N1) and a glial nuclear fraction (N2) have been isolated from 15-day-old rabbit cerebral cortex using the Thompson procedure. More than 56% of the homogenate DNA was recovered in the two nuclear fractions, with N1 being the larger by about eightfold. Fractions N1 and N2 had very similar phospholipid distributions, with phosphatidylinositol being a larger component than phosphatidylserine. Fatty acid analyses demonstrated that phosphatidylethanolamine and phosphatidylinositol, individually, had similar fatty acid profiles in fractions N1 and N2, and also in nuclear and microsomal fractions derived from homogenates of nerve cell bodies isolated from cortex of 15-day-old rabbits. In contrast, the nuclear phosphatidylcholines had lower levels of palmitate and higher levels of arachidonate than did microsomal phosphatidylcholines. Molecular species analyses indicated that monoenes (41 mol%), tetraenes (20 mol%), and saturates (13 mol%, composed chiefly of palmitate) were the principal classes of N1 phosphatidylcholines, while the diacyl species of phosphatidylethanolamine of this fraction were characterized by high levels of tetraenes (44 mol%), pentaenes (17 mol%), and hexaenes + polyenes (24 mol%). The neutral glycerides of fraction N1 occurred collectively at a level of 0.05 mol/mol phospholipid. Prominent fatty acids of diacylglycerols included palmitate (31%), oleate (20%), arachidonate (14%), and stearate (13%). Triacylglycerols showed a similar pattern but with relatively high levels of linoleate (11%), while monoacylglycerols consisted almost entirely of palmitate (33%), stearate (35%), and oleate (24%).  相似文献   

6.
High molecular weight, multicatalytic proteinases (named proteasomes) have been for the first time found, on the basis of different protein patterns, in the cytoplasmic soluble fractions of both non-hormone-treated (premature) and progesterone-treated (mature) oocytes of a frog (Rana pipiens).These enzymes, pooled separately as two fractions sedimenting between around 19S and the bottom (over 27S) on glycerol density gradient centrifugation, were composed of several molecular forms with apparent high molecular weights ranging from over 700 kDa, as judged on Sepharose 6B gel filtration. In addition, both the fractions hydrolyzed distinctly a Tyr-containing substrate in the presence of SDS as an activator, and exhibited higher activities toward Arg-containing substrates in the absence of SDS, and activity toward a Glu-containing substrate in the presence and absence of SDS. Immunological experiments using antibodies against proteasomes purified from ovaries of Xenopus laevis clearly revealed characteristic cross-reactivity with both the fractions found in Rana.These data suggest that these enzymes in the two fractions from the respective oocytes in Rana are very similar or identical to the proteasomes of Xenopus. The enzymes in premature oocytes eluted at 0.15–0.18M NaCl on a DEAE-cellulose column disappeared on treatment with TPCK, a well-known chymotrypsin inhibitor, suggesting that the 0.15–0.18M NaCl-eluate contained chymotrypsin-like proteinases probably latent in ovo. The enzymes in mature oocytes had not similar chromatographical patterns to those in premature oocytes.These results suggest that the enzymes already present in premature oocytes may be involved through conformational alterations as to the protein pattern in oocyte maturation following induction by progesterone.Abbreviations AMC 7-Amino-4-methylcoumarin - Boc t-Butyloxycarbonyl - Cbz Carbobenzoxy - GVBD Germinal Vesicle Breakdown - MCA 4-Methylcoumaryl-7-Amide - MPF Maturation Promoting Factor - NA 2-Naphthylamide - SDS Sodium Dodecyl Sulfate - Suc Succinyl - TPCK N-Tosyl-L-Phenylalanine Chloromethyl Ketone  相似文献   

7.
Double-stranded nucleic acids from a strain of Penicillium chrysogenum containing RNA viruses were isolated by agarose-gel filtration, and separated into DNA and double-stranded RNA fractions by agarose-gel chromatography in 2.5m-NaCl. The DNA fraction contained less than 1% alkali-labile polynucleotides, and sedimented homogeneously at 8-10S in alkaline sucrose gradients. In CsCl gradients it tended to band in the density region of 1.66-1.72g/ml. It had a ;melting' temperature (T(m)) of 75 degrees C in 0.015m-NaCl-0.0015m-trisodium citrate, corresponding to 51.5mol% of G+C. The double-stranded RNA fraction did not contain detectable DNA. It could not band in CsCl up to a density of 1.78g/ml, and mainly consisted of a 14-15S RNA species with a T(m) of 88.5 degrees C in the above solvent, and a G+C content of 49.3 mol%.  相似文献   

8.
R. Hampp 《Planta》1980,150(4):291-298
Purified intact protoplasts were isolated from etiolated and greening leaves of Avena sativa. They were ruptured by forcing them through a 20-m aperture nylon net and immediately thereafter fractionated into a pure pellet of plastids (well above 70% of total plastids), a layer of mitochondria only slightly contaminated by other cellular constituents (about 50% of total mitochondria), and a cytoplasmic supernatant. This was achieved within 60 s by an integrated method of homogenation of protoplasts and centrifugal filtration of the homogenate on a gradient of silicone oils, contained together with the nylon net in 450 l microtubes, and verified by comparing the levels of activity of specific markers within the three fractions obtained. With appropriate modifications to immediately quench metabolic reactions within the fractions, this method allows the determination of metabolite levels within plastids, mitochondria, and the cytoplasmic compartment of intact protoplasts. The applicability of this technique is demonstrated by the determination of ATP in the plastids, mitochondria, and the cytoplasm of protoplasts obtained from etiolated and greening primary leaves of Avena. The levels of ATP, corrected for contamination of the fractions by each other, exhibit a pronounced transient increase during greening, especially within the cytoplasm.Abbreviations BSA bovine serum albumin - Cyt c cytochrome c - EDTA ethylenediamine tetraacetic acid - HEPES N-2-hydroxyethyl-piperazine-N-2-ethane sulphonic acid - MES 2(N-morpholino) ethane sulphonic acid - PGA 3-phosphoglyceric acid - PEP phosphoenol pyruvic acid - RuBP ribulose-1.5-bis-phosphate  相似文献   

9.
The aim of this study was to elucidate the effect of various mole percentages (0-25 mol%) of 2000 Da polyethylene glycol-disteroylphosphoethanolamine (PEG-DSPE) in the presence or absence of 40 mol% cholesterol and the effect of degree of saturation of phosphatidylcholine (PC) on the size and the lipid bilayer packing of large unilamellar vesicles (LUV). Egg PC (EPC, unsaturated) LUV and fully hydrogenated soy PC (HSPC, saturated) LUV partial specific volume, specific compressibility, size, and packing parameter (PP) of lipids were characterized by measurements of density, ultrasonic velocity, specific turbidity, and dynamic light scattering. Liposome size and specific turbidity decreased with increase in temperature and PEG-DSPE mol%, except at 7+/-2 mol%. At this PEG-DSPE mol%, an anomalous peak in liposome size of 15+/-5 nm was observed. We attribute this effect mainly to the change in the spatial structure of the PEG-DSPE molecule, depending on whether the grafted PEG is in the mushroom or brush configuration. In the mushroom regime, i.e., when the grafted PEG is up to 4 mol% in LUV, the PEG moiety did not affect the additive PP of the lipids in the bilayer, and the PP value of PEG-DSPE is 1.044; while in the brush regime, i.e., when the grafted PEG is higher than 4 mol%, the PP of PEG-DSPE decreases exponentially, reaching the value of 0.487 at 30 mol% of grafted lipopolymer. The specific compressibility and additive PP values for the mixture of matrix lipid (EPC or HSPC), cholesterol, and PEG-DSPE for all liposome compositions investigated reached their maximum at 7+/-2 mol% PEG-DSPE, the concentration of PEG-DSPE at which the highest biological stability of the LUV is achieved.  相似文献   

10.
Water-soluble hemicelluloses were extracted from milled aspen wood (Populus tremula) employing microwave oven treatment at 180 degrees C for 10 min. The final pH of this extract was 3.5. From this extract oligo- and polysaccharides were isolated and subsequently fractionated by size-exclusion chromatography. The structures of the saccharides in three of the fractions obtained were determined by 1H and 13C NMR spectroscopy, using homonuclear and heteronuclear two-dimensional techniques. The polysaccharides present in the two fractions eluted first were O-acetyl-(4-O-methylglucurono)xylans. The average degree of acetylation of the xylose residues in these compounds was 0.6. The structural element -->4)[4-O-Me-alpha-D-GlcpA-(1-->2)][3-O-Ac]-beta-D-Xylp-(1 --> could also be identified. On the average, these two xylans were composed of the following (1-->4)-linked beta-D-xylopyranosyl structural elements: unsubstituted (50 mol%), 2-O-acetylated (13 mol%), 3-O-acetylated (21 mol%), 2,3-di-O-acetylated (6 mol%) and [MeGlcA alpha-(1-->2)][3-O-acetylated] (10 mol%). Most of the 4-O-methylglucuronyl and acetyl substituents in the isolated polysaccharides survived the microwave oven treatment. The third fraction, eluted last, contained acetylated xylo-oligosaccharides, with minor contamination by an acetylated mannan. In the case of these xylo-oligosaccharides, the average degree of acetylation was 0.3.  相似文献   

11.
Bacillus sp. 3B6, bacterium isolated from cloud water, was incubated on sucrose for exopolysaccharide production. Dialysis of the obtained mixture (MWCO 500) afforded dialyzate (DIM) and retentate (RIM). Both were separated by size exclusion chromatography. RIM afforded eight fractions: levan exopolysaccharide (EPS), fructooligosaccharides (FOSs) of levan and inulin types with different degrees of polymerization (dp 2–7) and monosaccharides fructose:glucose = 9:1. Levan was composed of two components with molecular mass ∼3500 and ∼100 kDa in the ratio 2.3:1. Disaccharide fraction contained difructose anhydride DFA IV. 1-Kestose, 6-kestose, and neokestose were identified as trisaccharides in the ratio 2:1:3. Fractions with dp 4–7 were mixtures of FOSs of levan (2,6-βFruf) and inulin (1,2-βFruf) type. DIM separation afforded two dominant fractions: monosaccharides with fructose: glucose ratio 1:3; disaccharide fraction contained sucrose only. DIM trisaccharide fraction contained 1-kestose, 6-kestose, and neokestose in the ratio1.5:1:2, penta and hexasaccharide fractions contained FOSs of levan type (2,6-βFruf) containing α-glucose. In the pentasaccharide fraction also the presence of a homopentasaccharide composed of 2,6-linked βFruf units only was identified. Nystose, inulin (1,2-βFruf) type, was identified as DIM tetrasaccharide. Identification of levan 2,6-βFruf and inulin 1,2-βFruf type oligosaccharides in the incubation medium suggests both levansucrase and inulosucrase enzymes activity in Bacillus sp. 3B6.  相似文献   

12.
In order to evaluate the mechanical properties of poly(lactate-co-3-hydroxybutyrate) [P(LA-co-3HB)] and its correlation with the LA fraction, P(LA-co-3HB)s with a variety of LA fractions were prepared using recombinant Escherichia coli expressing the LA-polymerizing enzyme and monomer supplying enzymes. The LA-overproducing mutant E. coli JW0885 with a pflA gene disruption was used for the LA-enriched polymer production. The LA fraction was also varied by jar-fermentor based fine-regulation of the anaerobic status of the culture conditions, resulting in LA fractions ranging from 4 to 47 mol%. In contrary to the opaque P(3HB) film, the copolymer films attained semitransparency depending on the LA fraction. Young's modulus values of the P(LA-co-3HB)s (from 148 to 905 MPa) were lower than those of poly(lactic acid) (PLA) (1020 MPa) and P(3HB) (1079 MPa). In addition, the value of elongation at break of the copolymer with 29 mol% LA reached 150%. In conclusion, P(LA-co-3HB)s were found to be a comparatively pliable and flexible material, differing from both of the rigid homopolymers.  相似文献   

13.
Bostrychia montagnei was submitted to aqueous extraction at 25 and 85 °C. The purified polysaccharide extracts represent ∼ 17% of the dried alga. Galactose is the principal monosaccharide component of these extracts (60.8–70.4 mol%). 3,6-Anhydrogalactose and its 2- O-methyl derivative are also present in smaller amounts (16.2–22.0 mol%), as well as other methylated sugars, such as 6- O- (6.5–7.8 mol%) and 2-O-methylgalactose (0.2–2.1 mol%). Xylose (4.1–8.1 mol%) and glucose (0.7–2.6 mol%) were also detected. The aqueous extracted polysaccharides (25 °C) were separated by anion-exchange chromatography into six sulphated galactan fractions with negative specific rotations and another two with high xylose contents and positive specific rotations. The sulphated galactans all have an agar type backbone modified by partial O-methyl substitution on O-6 or O-2 of the galactosyl units. The latter substitution is also present in varying degrees of 3,6-anhydrogalactose. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

14.
Four yellow-pigmented, gram-negative, chemoorganotrophic aerobic bacteria were isolated from starfish Stellaster equestris (strains 022-2-10T, 022-2-9, and 022-2-12) and soft coral (unidentified species) (strain 022-4-7) collected in the South China Sea. 16S rRNA gene sequence-based analyses of the new organisms revealed that Erythrobacter spp. were the closest relatives and shared the highest similarity of 98.7% to E. citreus, 98.5% to E. flavus, 97.9% to E. litoralis and 97.6% to E. longus. The novel organisms were tolerant to 3-6% NaCl, grew between 10 degrees C and 40 degrees C, and were not able to degrade gelatin, casein, and agar, while degraded Tween 80. Two strains (022-2-9 and 022-2-12) could weakly degrade starch. All strains produced a large pool of carotenoids and did not have Bacteriochlorophyll a. Phosphatidylethanolamine (30-36%), phosphatidylglycerol (39-46%), and phosphatidylcholine (21-27%) were the predominant phospholipids. Sphingoglycolipid was not detected. The major fatty acids were 16:0 (6-11%), 16:1omega7 (12-15%), and 18:1omega7 (46-49%). The two-hydroxy fatty acids, 13:0-2OH, 14:0-2OH, 15:0-2OH, 16:0-2OH were also present. The G + C content of the DNAs ranged from 61 to 62 mol%. The level of DNA similarity among four strains was conspecific and ranged from 94% to 98%. Even though new strains and other species of the genus had rather high level of 16S rRNA gene sequence similarities, DNA-DNA hybridization experiments showed only 33-39% of binding with the DNA of the type strains. On the basis of these results and the significant differences demonstrated in the phenotypic and chemotaxonomic characteristics, it is suggested that the new organisms be classified as a novel species; the name Erythrobacter vulgaris sp. nov. is proposed. The type strain is 022-2-10T (= KMM 3465T = CIP 107841T).  相似文献   

15.
Six isolates of novel marine myxobacteria, designated strains SHK-1T, SMK-1-1, SMK-1-3, SMK-10, SKK-2, and SMP-6, were obtained from various coastal samples (mud, sands and algae) collected around Japan. All of the isolates had Gram-negative rod-shaped cells, motile by gliding and grew aerobically. They showed bacteriolytic action, fruiting body formation, and NaCl requirement for growth with an optimum concentration of 1.0-2.0% (w/v). In addition, divalent cationic components of seawater, such as Mg2+ or Ca2+, were also needed for growth. The major respiratory quinone was MK-7. The G+C content of genomic DNA ranged from 65.6 to 67.4 mol% (by HPLC). The isolates shared almost identical 16S rDNA sequences, and clustered with a recently described marine myxobacterium, Plesiocystis pacifica, as their closest relative on a phylogenetic tree (95.9-96.0% similarity). Physiological and chemotaxonomic differences between the new strains and strains of the genus Plesiocystis justify the proposal of a new genus. Therefore, we propose to classify the six isolates into a new taxon of marine myxobacteria with the name, Enhygromyxa salina gen. nov., sp. nov. The type strain is SHK-1(T) (JCM 11769(T) = DSM 15217(T) = AJ 110011(T)).  相似文献   

16.
The leishmanicidal effect of crude ethanolic extract of stem bark of Dysoxylum binectariferum and its fractions has been investigated against Leishmania donovani, the causative agent of visceral leishmaniasis. Ethanolic extract was lethal to promastigotes as well as amastigote forms in macrophage system at the concentration of 100 microg/ml. Chloroform fraction significantly inhibited promastigote multiplication and was also active against amastigotes in infected J774A.1 macrophages at 100 microg/ml. Hexane fraction was moderately active and the other fractions were inactive against both the forms. When tested in vivo in hamsters, ethanolic extract was toxic at 500 mg/kg whereas exhibited marginal activity (67.7+/-5.3%) at 250 mg/kg x 5, p.o. on day 7 post treatment (p.t.) which increases slightly (69+/-4.7) by day 30 p.t. Chloroform and n-hexane fractions exhibited 64.3+/-4% and 47.8+/-4.6% parasite inhibition at the dose of 100 mg/kg x 5 p.o., respectively. The pure compound, rohitukine, obtained from chloroform fraction showed weaker in vitro activity and was ineffective in infected hamsters. The lead potential of this plant need further investigations.  相似文献   

17.
To study lipid breakdown in brain membranes following hemorrhage, synaptosome and myelin fractions isolated from rat brain were incubated with rat serum. After 3 h in vitro at 37 degrees C, 0.43 and 0.26 mumol of fatty acid were released in incubations containing synaptosomes (1.37 mumols phospholipid) or myelin (1.23 mumols phospholipid), respectively, in the presence of 0.25 mL serum. Less than 0.05 mumol of fatty acid was liberated in incubations containing only serum, synaptosomes, or myelin. For synaptosomes and serum, docosahexaenoate was the principal fatty acid released (28 mol% of total) after 3 h of incubation. This fatty acid and arachidonate made up 43 mol% of the liberated fatty acid. The presence of free docosahexaenoate was of interest, as this fatty acid is particularly enriched in phosphatidylserine and phosphatidylethanolamine, phospholipids found in the cytoplasmic half of the synaptosomal plasma membrane and in interior synaptosomal membranes. In incubations of serum and myelin, oleate was the major free fatty acid produced in 30 min to 3 h of incubation (29-35 mol% of total). After 3 h, docosahexaenoate contributed 20 mol% to the total. The release of fatty acids from the membranes may be mediated by serum phospholipase(s) or possibly by activated endogenous lipolytic activities.  相似文献   

18.
Skin secretions of the frog Agalychnis litodryas were evaluated for the isolation and characterisation of novel insulinotropic peptides. Crude secretions obtained from young adult frogs by mild electrical stimulation of the dorsal skin surface were purified by reverse-phase high-performance liquid chromatography (HPLC) yielding 70 fractions. In acute 20-min incubations with glucose responsive BRIN-BD11 cells, fractions 39-42 (band 1) and fractions 44-46 (band 2) significantly stimulated insulin release by 2-3.5-fold compared with 5.6 mM glucose alone. Pooled fractions in band 1 and band 2 were rechromatographed to reveal 20 homogenous peptide peaks, which elicited significant 1.5-4-fold increases in insulin release. Mass spectrometry analyses indicated molecular masses of between 1649.2 and 4988.9 Da. The two peptides with the greatest insulin-releasing activity were directly subjected to N-terminal amino acid sequence analysis. The sequence of the 3020 Da peptide, called frog skin insulinotropic peptide or FSIP, was determined as AVWKDFLKNIGKAAGKAVLNSVTDMVNE, which has 79% homology with the C-terminal of the 75 amino acid dermaseptin BIV precursor. A partial N-terminal sequence was determined for the 2546.2 Da peptide as MLADVFEKIMGD... These data indicate that the skin secretions of A. litodryas frogs contain biologically active peptides which merit further evaluation as a new class of insulin secretagogues.  相似文献   

19.
In a previous study, we observed a series of dips in the plot of E/M (the ratio of excimer to monomer fluorescence intensity) versus the mole fraction of 1-palmitoyl-2-(10-pyrenyl)decanoyl-sn-glycerol-3-phosphatidylcholine (Pyr-PC) in Pyr-PC/DMPC binary mixtures at 30 degrees C. In the present study, we have characterized the physical nature of E/M dips in Pyr-PC/DMPC binary mixtures by varying pressure, temperature, and vesicle diameter. The E/M dips at 66.7 and at 71.4 mol% PyrPC in DMPC multilamellar vesicles remain discernible at 30-43 degrees C. At higher temperatures (e.g., 53 degrees C), the depth of the dip abruptly becomes smaller. This result agrees with the idea that E/M dips appear as a result of regular distribution of pyrene-labeled acyl chains into hexagonal super-lattices at critical mole fractions. Regular distribution is a self-ordering phenomenon. Usually, in self-ordered systems, the number of structural defects increases with increasing temperature, and thermal fluctuations eventually result in an order-to-disorder transition. The effect of vesicle diameter on the E/M dip at 66.7 mol% Pyr-PC in DMPC has been studied at 37.5 degrees C by using unilamellar vesicles of varying sizes. The E/M dip is observable in large unilamellar vesicles; however, the depth of the E/M dip decreases when the vesicle diameter is reduced. When the vesicle diameter is reduced to about 64 nm, the dip becomes shallow and split. This result suggests that the curvature-induced increase in the separation of lipids in the outer monolayer decreases the tendency of regular distribution for pyrene-labeled acyl chains. Regular distribution is believed to arise from the long-range repulsive interaction between Pyr-PC molecules due to the elastic deformation of the lipid matrix around the bulky pyrene moiety. When the radius of curvature becomes small, outer monolayer lipids are more separated. Therefore, pyrene-containing acyl chains fit better into the membrane matrix, which alleviates the deformation of the lattice and diminishes the long-range repulsive interactions between pyrene-containing acyl chains. Furthermore, we have shown a striking difference in the pressure dependence of E/M at critical Pyr-PC mole fractions and at noncritical mole fractions. In the pressure range between 0.001 and 0.7 kbar at 30 degrees C, E/M decreases steadily with increasing pressure at noncritical mole fractions; in contrast, E/M changes little with pressure at critical mole fractions (e.g., 33.3 and 50.0 mol% Pyr-PC).(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

20.
An aggregate-attached bacterium, strain 88/2-7, was isolated from samples of the Southern Ocean and investigated in a polyphasic approach. The novel marine isolate is an aerobic, Gram-negative, oxidase- and catalase-positive, non-motile short rod and grows in form of cream-colored colonies. Growth was observed at 5-35 degrees C. The bacterium tolerated concentrations of 0-13% (w/v) NaCl and utilized a relatively restricted spectrum of carbon sources. The analysis of the fatty acids revealed 18:1 cis 9 (18:1omega9c) as main fatty acid. The G+C content of the DNA was approximately 42 mol%. The sequence of the 16S rDNA assigned strain 88/2-7 to the gamma-subclass of Proteobacteria with a similarity of 99.65% to Psychrobacter proteolyticus (DSM 13887T). A DNA-DNA-hybridization study showed only 26.8% renaturation to the respective strain. Based on the morphological, physiological and molecular properties of the new isolate, the name Psychrobacter nivimaris sp. nov. (type strain 88/2-7T) is proposed.  相似文献   

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