Structure and conformation of peptides involving prolyl residue III. L-Prolyl-L-isoleucine monohydrate

The dipeptide, L-prolyl-L-isoleucine monohydrate (C₁₁ H₂₀N₂O₃· H₂O, molecular weight 246.3) crystallizes in the monoclinic space group P2₁, with a = 6.601(3)Å, b = 5.413(3) Å, c = 19.128(6) Å, β= 98.1(1)°, Z = 2, Do = 1.20g·cm^-3 and Dc = 1.208g·cm^-3. The structure was solved by MULTAN–80 and refined to a final R-factor of 0.081 for 594 reflections measured on a Enraf Nonius CAD-4 diffractometer. The peptide linkage exists in the trans conformation. The pyrrolidine ring is disordered with two alternate envelope conformations for the C^γ atom. The values of the sidechain torsion angles are: χ₁₁=– 63.6(17)°, χ₁₂= 171.1(16)° and χ₂=– 59.6(21)° for isoleucine (C-terminal). The crystal structure is stabilized by a three-dimensional network of N—H ? O, O—H ? O and C—H ? O hydrogen bonds. The dipeptide exists in the extended Conformation.     

单发转移性肝癌的诊断和治疗

目的　探讨单发转移性肝癌的诊断和治疗。方法　回顾性总结分析 1年半来治疗 1 0例患者的临床资料。结果1 0例患者入院后确诊为转移性肝癌 ,肝脏转移灶均为单发 ,肿瘤直径在 4 .5～ 1 2 .4 cm ,平均 7.8± 2 .5 cm。 2例来自胃癌 ,7例来自结直肠癌 ,1例来自恶性淋巴瘤 ,门诊误诊率高达 6 0 %。 9例患者均同期行肝转移癌切除及胃肠道肿瘤切除术 ,手术顺利 ,无 1例出现手术并发症。结论　单发肝转移癌发病率低 ,容易误诊 ,医师对本病认识不足以及临床思维的局限是导致误诊的主要原因。治疗首选肝转移灶和原发灶肿瘤同期切除     

继发性骨质疏松防治的研究

目的总结继发性骨质疏松预防与治疗的经验及提出见解.方法用钙代谢平衡的方法研究了钙代谢的基本情况,比较了补钙与不补钙在若干种生理状态对骨密度的影响,总结继发性骨质疏松的病因及对其采取不同方法的治疗经验.结果中国人膳食含钙量属于正常范围低水平状态,与适宜摄入量(AI)比较是不足的,在一定的生理状态下应予补钙.缺钙是原发性骨质疏松与继发性骨质疏松的不利因素.氟中毒骨病、糖尿病、性腺功能减退、肿瘤、糖皮质激素过多和甲亢均有其各别的病理生理,导致继发性骨质疏松,防治方法各异.结论从胚胎至老年都应防治骨质疏松.不同情况采取方法各异,但有效.     

The universal algorithm of maturation for secretory and excretory protein precursors.

During maturation, most proteins undergo different posttranslational modifications. In most simple cases, signal peptidases remove the signal or leader peptide from the precursors of the secretory proteins during their translocation across the ER membrane. For biologically active proteins, such as enzymes, regulatory and defense proteins, toxins, etc., additional maturation-regulating mechanisms were shown to proceed with limited proteolysis of inactive precursors by specific enzymes. A number of specific enzymes from different cell types selectively cleave proproteins at specific processing sites. In this work, we analyzed the sequences of protein precursors synthesized in the excretory glands of different animals and identified new, non-traditional processing sites. They differ from the motifs previously identified in secreted proteins' precursors and enabled us to reconstruct the sequence of events leading to the conversion of protein precursors into the final products (mature proteins). We also found that in animals, the maturation mechanism of secretory and excretory proteins and the set of enzymes involved are species specific. The processing sites identified in protein precursors in this study are useful for a more detailed genome analysis and more accurate mature protein sequence prediction.     

Gender differences in informal caring

Men have hitherto largely been invisible in research on informal care. This paper examines gender differences in informal caring, focusing on gender differences according to the relationship between the carer and care-recipient and the location of caring. The paper uses secondary analysis of the 1990–91 General Household Survey, which identified over 2700 adults as informal carers. Four per cent of men and women provide care for someone living in the same household. More women than men, 13% compared with 10%, provide care for someone living in another household. Men carers are less involved in care provision than women, providing fewer hours of care each week, and are less likely to be the main carer. However, gender differences are most marked among married carers, apart from those caring for their spouse, and least among unmarried carers. Married men can often rely on their wives to perform caring roles rather than performing them personally. Women carers are more likely to provide personal care than men carers, but the gender difference is least among those caring for their spouse or for disabled children. Cross-sex personal care is performed within the marital relationship and by parents caring for disabled children, but seldom by adult children caring for their parents or in more distant caring relationships. Evidence of cross-sex taboos in giving personal care is largely restricted to care provided in another household. Since the majority of elderly people in need of care are women, such cultural taboos may reinforce the pressure on mid-life women to care for mothers and mothers-in-law.     

Interaction of glucagon with artificial lipid bilayer membranes

The enhancement of fluorescence emission from the tryptophan residue of glucagon, the quenching of that emission with acrylamide and with 5-doxyl and 16-doxyl stearic acid, circular dichroism spectra, the release of 6-carboxytluorescein, and polarized infrared attenuated total reflection (IR-ATR) spectra were used to study the interaction of glucagon with intact lipid vesicles and flat bilayers. Dimyristoylphosphatidylcholine bound the peptide only below the main transition temperature, thus confirming earlier results of Epand et al. (1977). However, the peptide is also bound by vesicles of unsaturated lipids above their transition temperature, suggesting an influence of lipid area on the binding process. Circular dichroism showed that binding to such vesicles also increases the helix content of glucagon. The IR-ATR study and a comparison with dynorphin-A-(I-13)-tridecapeptide revealed profound differences in orientation of the two peptides. The dichroic ratios and the derived order parameters indicated an isotropic orientation of the helical segments of glucagon, but did not exclude a principal orientation of the molecules lying flat on the nienibrane surface. In contrast, the axis of the dynorphin helix is clearly oriented normal to the interface. The two peptides also differ in their rates of 6-carboxyfluorescein release, suggesting a deeper penetration of the primary amphiphilic helix of dynorphin A-(I-13) than of the secondary amphiphilic helix of glucagon.     

Complete structure of eclosion hormone of Manduca sexta

The locations of the three disulfide bonds of eclosion hormone (EH) isolated from Manduca sexta were assigned by sequence analysis of thermolysin fragments and by comparison of a key heterodimeric fragment to regiospecifically synthesized parallel and antiparallel isomers. We elucidated the complete structure of Manduca EH as a 62-residue peptide which has three disulfide bonds between Cys¹⁴-Cys³⁸, Cys¹⁸-Cys³⁴, and Cys²¹-Cys⁴⁹.     

茶叶多糖的研究进展

茶叶多糖是一种复合杂多糖，具有许多生物活性。作者系统地介绍了茶叶多糖的提取、分离、纯化、纯度鉴定及相对分子质量测定的方法，以及其含量和组成、理化性质、化学结构及空间构象、生物活性等方面的研究进展，并对上述方法及研究进展进行了分析和评述。     

Transplant data: sources, collection and research considerations, 2004

The process of collecting and analyzing transplant data is complex. Familiarity with how these data are collected is crucial to a thorough understanding of the information. This article focuses on available OPTN-SRTR data and the continuing evolution of data collection mechanisms; how that data collection system is improving the data quality and reducing the data collection burden; how additional ascertainment of outcomes both completes and validates existing data; and caveats that remain for researchers. This year's article focuses further on research considerations related to cohort choice, timing of data submission, and potential biases in follow-up data. Ongoing improvements in data collection timeliness and scope are covered. The impact of extra ascertainment of outcomes, particularly for post-transplant kidney graft failure from Medicare data, are also examined. A section on graft failure reporting among different sources traces the steps by which the SRTR reconciles different data sources in its analyses. It is important that those reading and conducting transplant research understand the origin, structure, and scope of the available data. All of these issues should be carefully considered when choosing cohorts and data sources for analysis.