Chain conformation and bioactivity of water‐soluble polysaccharide extracted from Rhizoma Panacis Japonici

A water‐soluble α‐(1→4)‐D ‐glucan heteropolysaccharide with 37% degree of branch extracted by base from Rhizoma Panacis Japonici, coded as RPS3, was fractionated into six fractions by the method of nonsolvent addition. Their weight‐average molecular mass (M_w), polydispersity index (M_w/M_n), and radius of gyration (〈s²〉_z^1/2) were determined with laser light scattering (LLS) and size exclusion chromatography combined with LLS. The structure of the fraction was determined by methylation analyses and ¹³C NMR. The dependences of intrinsic viscosity ([η]) and 〈s²〉_z^1/2 on M_w were established as [η] = 0.71 M_w^{0.27 ± 0.01} (cm³/g) and 〈s²〉_z^1/2 = 1.53 M_w^{0.27 ± 0.02} (nm) in the M_w range from 5.62 × 10⁴ to 3.05 × 10⁶ (g/mol) for RPS3 in 0.15M NaCl aqueous solution at 25°C. On the basis of the current theory of the polymer solution, the fractal dimension (d_f), unperturbed chain dimension (A), and characteristic ratio (C_∞) were calculated to be 3.0, 1.48 Å, and 15.1, respectively. The results revealed that the RPS3 chains existed as spherical conformation in the aqueous solution. Transmission electron microscope further provided the evidence of the sphere shape of the RPS3 and its fractionated molecules in water. In vitro cytotoxicity assay indicated that the fractions could inhibit the tumor cells and showed no harm to normal cells at low dose. The bioactivity was relative with molecular mass of the samples. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 383–390, 2010. This article was originally published online as an acceptedpreprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office atbiopolymers@wiley.com     

Conformation Changes,N-terminal Involvement,and cGMP Signal Relay in the Phosphodiesterase-5 GAF Domain

The activity of phosphodiesterase-5 (PDE5) is specific for cGMP and is regulated by cGMP binding to GAF-A in its regulatory domain. To better understand the regulatory mechanism, x-ray crystallographic and biochemical studies were performed on constructs of human PDE5A1 containing the N-terminal phosphorylation segment, GAF-A, and GAF-B. Superposition of this unliganded GAF-A with the previously reported NMR structure of cGMP-bound PDE5 revealed dramatic conformational differences and suggested that helix H4 and strand B3 probably serve as two lids to gate the cGMP-binding pocket in GAF-A. The structure also identified an interfacial region among GAF-A, GAF-B, and the N-terminal loop, which may serve as a relay of the cGMP signal from GAF-A to GAF-B. N-terminal loop 98–147 was physically associated with GAF-B domains of the dimer. Biochemical analyses showed an inhibitory effect of this loop on cGMP binding and its involvement in the cGMP-induced conformation changes.     

Spectroscopic and Functional Characterizations of Cyanobacterium Synechocystis PCC 6803 Mutants on and near the Heme Axial Ligand of Cytochrome b559 in Photosystem II

The functional role of cytochrome (cyt) b₅₅₉ in photosystem II (PSII) was investigated in H22Kα and Y18Sα cyt b₅₅₉ mutants of the cyanobacterium Synechocystis sp. PCC6803. H22Kα and Y18Sα cyt b₅₅₉ mutant carries one amino acid substitution on and near one of heme axial ligands of cyt b₅₅₉ in PSII, respectively. Both mutants grew photoautotrophically, assembled stable PSII, and exhibited the normal period-four oscillation in oxygen yield. However, both mutants showed several distinct chlorophyll a fluorescence properties and were more susceptible to photoinhibition than wild type. EPR results indicated the displacement of one of the two axial ligands to the heme of cyt b₅₅₉ in H22Kα mutant reaction centers, at least in isolated reaction centers. The maximum absorption of cyt b₅₅₉ in Y18Sα mutant PSII core complexes was shifted to 561 nm. Y18Sα and H22Kα mutant PSII core complexes contained predominately the low potential form of cyt b₅₅₉. The findings lend support to the concept that the redox properties of cyt b₅₅₉ are strongly influenced by the hydrophobicity and ligation environment of the heme. When the cyt b₅₅₉ mutations placed in a D1-D170A genetic background that prevents assembly of the manganese cluster, accumulation of PSII is almost completely abolished. Overall, our data support a functional role of cyt b₅₅₉ in protection of PSII under photoinhibition conditions in vivo.     

Structural Variants Selected during Yak Domestication Inferred from Long-Read Whole-Genome Sequencing

Structural variants (SVs) represent an important genetic resource for both natural and artificial selection. Here we present a chromosome-scale reference genome for domestic yak (Bos grunniens) that has longer contigs and scaffolds (N50 44.72 and 114.39 Mb, respectively) than reported for any other ruminant genome. We further obtained long-read resequencing data for 6 wild and 23 domestic yaks and constructed a genetic SV map of 372,220 SVs that covers the geographic range of the yaks. The majority of the SVs contains repetitive sequences and several are in or near genes. By comparing SVs in domestic and wild yaks, we identified genes that are predominantly related to the nervous system, behavior, immunity, and reproduction and may have been targeted by artificial selection during yak domestication. These findings provide new insights in the domestication of animals living at high altitude and highlight the importance of SVs in animal domestication.     

中华大蟾蜍卵母细胞质膜存在钙依赖性的氯离子通道

本文采用双微电极电压钳方法研究了中华大蟾蜍卵母细胞内源性电压门控型离子通道的成分及其生理特性。卵母细胞去极化至 -30 mV 及更正电压时,有一持续的电压依赖性外向电流出现。钾离子通道拮抗剂四乙基氯化氨(tetraethy-lammonium chloride, TEA, 10 mmol/L)和 4- 氨基吡啶(4-aminopyridine, 4-AP, 10 mmol/L)协同作用时,该电流只能被抑制到最大电流幅度的(23.4±0.72)%。但是,上述浓度的TEA和4-AP 与氯离子通道拮抗剂5- 硝基-2, 3- 苯酚丙胺苯甲酸盐 (5-nitro-2,3-phenypropylamino benzoate, NPPB, 30 μmol/L)、无钙 Ringer 氏液或钙离子通道拮抗剂维拉帕米(40 μmol/L)协同作用时,可分别将此外向电流抑制到最大电流幅度的(2.1±0.08)%、(2.2±0.04)% 和(3.1±0.15)%。结果表明,中华大蟾蜍卵母细胞质膜上除有钾离子电流之外,还存在钙依赖性的氯离子电流。     

自发性高血压大鼠多组织炎症状态

高血压是一种慢性血管性疾病,易累及肾、肝、心、脑等组织,引起脑卒中和心、肾损害等并发症.本研究对高血压时肾、肝、心、脑等组织的炎症状态进行了观察.实验采用自发性高血压大鼠(spontaneously hypertensive rat,SHR)和正常血压的Wistar-Kyoto(WKY)大鼠,用RT-PCR和Western blot法观察肾、肝、心、脑等组织炎症相关因子IL-1p、TNFα、ICAM-1、iNOS、C/EBPδ和PPARγ的基因表达;紫外分光光度法观察蛋白质羰基化水平和FRAP法检测组织总抗氧化能力.结果显示(1)SHR组织炎症相关因子表达较对照WKY增强,除IL-1βmRNA在肝和脑的增加不明显外,其余均有显著性差异(P＜0.05);(2)SHR和WKY大鼠肾、心、脑蛋白质羰基化水平(nmol/mg蛋白)分别为8.93±1.08和2.27±0.43、2.23±0.23和0.17±0.02、13.42±1.10和5.72±1.01,SHR明显增加(P＜0.05);而肝脏蛋白质羰基化水平无明显变化;(3)SHR肾、肝、心、脑总抗氧化能力水平显著低于WKY大鼠(P＜0.05).以上结果表明,SHR多个组织(肾、肝、心和脑)均存在炎症因子被诱导和氧化应激反应等明显的炎症状态,提示炎症可能在高血压及其并发症的病理改变中起重要作用.