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Ca2+-induced transformation of phosphatidylcholine-phosphatidic acid vesicles to larger bilayer structures has been examined using nuclear magnetic resonance, electron microscopy, gel permeation and radioisotope tracer techniques. For concentrated vesicle preparations where phosphatidic acid content remains less than 50% of total lipid, transformation to larger well defined unilamellar structures can be induced. The size of the product formed is dependent on phosphatidic acid content and on Ca2+ content when Ca2+ levels are between 0.3 and 1.0 mol ratios with respect to phosphatidic acid. During transformation bilayer composition remains unchanged and internal contents are retained in the final structure. These properties are indicative of concerted two vesicle and multiple vesicle fusions. The controllable and concerted fusions make the phosphatidic acid system suitable for further mechanistic studies. 相似文献
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Ta-Hsiu Liao 《Phytochemistry》1977,16(10):1469-1474
A deoxyribonuclease (DNase), similar to bovine pancreatic DNase, has been isolated from germinating barley. Commerically available malt was used as source of the enzyme. The purification procedure involves (a) ammonium sulfate fractionation (45–65% saturation), (b) CM-cellulose chromatography at pH 4.7 and (c) DEAE-cellulose chromatography at pH 8. DEAE-cellulose separates the enzyme into 4 distinct forms, designed as DNases A, B, C, and D. DNase A and B may be rechromatographed on DEAE-cellulose employing a CaCl2 instead of Tris-HCl gradient. Both forms appear homogeneous on regular and sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. In addition, both forms have a sp. act. of ca 700 units per A unit at 280 nm, similar to the potency of the pancreatic enzyme. DNase C and D, which are present in relatively small quantities in malt, were not characterized. The MWs of DNases A and B, as estimated by the SDS gel electrophoresis techniques, are near 32 000, slightly larger than that of the pancreatic enzyme. In the presence of either Mn2+ or Mg2+, the pH-activity profile of the barley enzyme is similar to that obtained with the pancreatic enzyme. Like the pancreatic enzyme, barley DNase is protected by Ca2+ from inactivation. The amino acid compositions of the A and B forms are about the same; a comparison of the malt and pancreatic enzymes shows many similarities but major differences in the amounts of glutamic acid, proline and glycine. The hydrolysis products of DNA by malt DNase are indistinguishable from those obtained with pancreatic DNase. Further hydrolysis of these products by snake venom phosphodiesterase shows malt DNase to be a 5′-phosphate producer. Deoxythymidine 3′,5′-di-p-nitrophenyl phosphate, one of the synthetic substrates of pancreatic DNase, is also hydrolysed by malt DNase. 相似文献
66.
Albert M. Wu Elvin A. Kabat Miercio E.A. Pereira Flavio G. Gruezo Jerry Liao 《Archives of biochemistry and biophysics》1982,215(2):390-404
Carbohydrate structures in the interior of a blood group A active substance (MSS) were exposed by one and by two Smith degradations. Reactivities of the original glycoprotein and its Smith degraded products with 13 different lectins and with anti-I Ma were studied by quantitative precipitin assay. MSS and its first Smith degraded product completely precipitated Ricinus communis hemagglutinin with five times less of the first Smith degraded glycoprotein being required for 50% precipitation. The second Smith degraded material precipitated only 90% of the lectin. MSS did not precipitate peanut lectin, whereas its first and second Smith degraded products completely precipitated the lectin. The first Smith degraded glycoprotein also reacted well with Wistaria floribunda, Maclura pomifera, Bauhinia purpurea alba, and Geodia lectins indicating that its carbohydrate moiety could contain dGalNAc, dGalβ1 → 3dGalNAc, dGalβ1 → 4dGlcNAc, dGalβ1 → 3dGlcNAcβ1 → 3dGal and/or dGalβ1 → 4dGlcNAcβ1 → 6dGal and/or dGalβ1 → 4dGlcNAcβ1 → 6dGalNAc determinants at nonreducing ends. The second Smith degraded material precipitated well with Ricinus communis hemagglutinin, Arachis hypogaea, Geodia cydonium, Maclura pomifera, and Helix pomatia lectins showing that dGalNAc, dGalβ1 → 3dGalNAc, dGalβ1 → 4dGlcNAc residues at terminal nonreducing ends could be involved. Monoclonal anti-I Ma (group 1) serum reacted strongly with the first Smith degraded product indicating large numbers of anti-I Ma determinants, dGalβ1 → 4dGlcNAcβ1 → d 6dGal and/or dGalβ1 → 4dGlcNAcβ1 → 6dGalNAc at nonreducing ends. The comparable activities of the native and Smith degraded products with wheat germ lectin indicate capacity to react with DGlcNAc residues at nonreducing ends and/or at positions in the interior of the chain. The totality of lectin reactivities indicates heterogeneity of the carbohydrate side chains. Oligosaccharides with 3H at their reducing ends released from the protein core of the first and second Smith degraded products were obtained by treatment with 0.05 m NaOH and 1 M NaB3H4 at 50 °C for 16 h (Carlson degradation). The liberated reduced oligosaccharides were fractionated by dialysis, followed by retardion, Bio-Gel P-2, P-4, and P-6 columns. They were further purified on charcoal-celite columns, and by preparative paper chromatography and high-pressure liquid chromatography. Their distribution by size was estimated by the yields on dialysis, Bio-Gel P-2, and Bio-Gel P-6 chromatography, and from the radioactivity of the reduced sugars. Of the oligosaccharide fractions from the first Smith degraded product, about 77% of the carbohydrate side chain residues contained from 1 to 6 sugars, 13% from 7 to perhaps 12 sugars, and 10% was nondialyzable (polysaccharides and glycopeptide fragments). Of the second Smith degraded product, approximately 82% of carbohydrate residues had from 1 to 6 sugars, 14% from 7 to perhaps 20 sugars and 4% was nondialyzable. The biological activity profile of the two Smith degraded products together with the size distributions of the oligosaccharides indicated that their carbohydrate side chains, comprised a heterogeneous population ranging in size from 1 to about 12 sugars. When most of these chains that are shorter than hexasaccharides are fully characterized it may be possible to reconstruct the overall structure of the carbohydrate moiety of the blood group substances and account for their biological activities. 相似文献
67.
葡萄籽油和饼粕的化学成分及特性研究 总被引:3,自引:0,他引:3
廖德胜;王敬勉;王章莉;粟巧功;陈基国 《武汉植物学研究》1991,9(2):181-184
本文报道了葡萄耔油和饼粕的化学组成及特性。经测定,葡萄籽中粗蛋白、脂肪和纤维素的含量分别为8.4%、15.0%和37.2%;葡萄籽油中,不饱和脂肪酸为89.6%,其中亚油酸占72—76%,碘值、皂化值和酸值分别为138.3、191.5和1.68。我们还对重要矿物元素Ca、Mg和K的含量进行了测定。在葡萄酿酒后的下脚料中,葡萄籽占20—26%,对其进行二次深加工,不仅可以减少环境污染,还可以增加社会经济效益。 相似文献
68.
本文以根盒试验与盆栽试验相结合的方法,研究了红壤性水稻土、淀浆白土、第四纪红土和赤红壤植稻后根际微生态系统中Si、Fe、Mn和Al等元素的状况及其与水稻生长的关系。结果表明,新垦红壤植稻后根际中活性Fe和Al富集;活性Mn量降低,但亏缺率小;活性Si则亏缺不明显,有时甚至富集。而熟化水稻土植稻后根际中活性Fe和Al则出现亏缺;Mn的亏缺较大,且差值明显;活性Si的亏缺现象更为显著。由于新垦红壤植稻后Fe和Al在根际微生态系统中富集,根茎叶中累积量较高,从而使Si、P和Mn等元素的吸收受阻,导致新垦红壤上水稻生长明显比熟化水稻土上的水稻要差。 相似文献
69.
Proline uptake can be mediated by three different transport systems in wild-type Salmonella typhimurium: a high-affinity proline transport system encoded by the putP gene and two glycine-betaine transport systems with a low affinity for proline encoded by the proP and proU genes. However, only the PutP permease transports proline well enough t allow growth on proline as a sole carbon or nitrogen source. By selecting for mutations that allow a putP mutant to grow on proline as a sole nitrogen source, we isolated mutants (designated proZ) that appeared to activate a cryptic proline transport system. These mutants enhanced the transport of proline and proline analogs but did not require the function of any of the known proline transport genes. The mutations mapped between 75 and 77.5 min on the S. typhimurium linkage map. Proline transport by the proZ mutants was competitively inhibited by isoleucine and leucine, which suggests that the ProZ phenotype may be due to unusual mutations that alter the substrate specificity of the branched-chain amino acid transport system encoded by the liv genes. 相似文献
70.
Prostatic ductal system in rats: regional variation in morphological and functional activities 总被引:9,自引:0,他引:9
The rat prostate is a complex ductal system with branches and subbranches extending from one end to another. Owing to the relative distance of various regions of the duct from the urethra, the entire length of the ductal system can be arbitrarily divided into three segments, i.e., the proximal, intermediate, and distal segments. The present study was carried out to assess the regional variation in cellular activities in this ductal system. Ventral prostates from adult Sprague-Dawley rats were dissected so that an individual ductal system was mechanically isolated and longitudinally sectioned to reveal various segments. Epithelial cells lining distal segments were tall-columnar type and were actively engaging in mitotic activity. Cells in intermediate segments were also tall-columnar type. However, they were mitotically quiescent, but able to produce secretory proteins. Evidence of programmed cell death was not observed in either of these two segments. Cells in proximal segments, on the other hand, were low-columnar or cuboidal in shape and were stained heavily for cathepsin D, a marker associated with late manifestation of cell death. Following castration in adult rats, there was a reversal in the site of programmed death in cells lining the ductal system. By Day 4 post-castration, distal segments contained many epithelial cells with intense cytoplasmic staining for cathepsin D while proximal segments showed a reduction in number of positively stained cells. By Day 7 post-castration, cells in proximal segments, though atrophied, were devoid of staining for cathepsin D.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献