Structural diversity in a human antibody germline library

To support antibody therapeutic development, the crystal structures of a set of 16 germline variants composed of 4 different kappa light chains paired with 4 different heavy chains have been determined. All four heavy chains of the antigen-binding fragments (Fabs) have the same complementarity-determining region (CDR) H3 that was reported in an earlier Fab structure. The structure analyses include comparisons of the overall structures, canonical structures of the CDRs and the VH:VL packing interactions. The CDR conformations for the most part are tightly clustered, especially for the ones with shorter lengths. The longer CDRs with tandem glycines or serines have more conformational diversity than the others. CDR H3, despite having the same amino acid sequence, exhibits the largest conformational diversity. About half of the structures have CDR H3 conformations similar to that of the parent; the others diverge significantly. One conclusion is that the CDR H3 conformations are influenced by both their amino acid sequence and their structural environment determined by the heavy and light chain pairing. The stem regions of 14 of the variant pairs are in the ‘kinked’ conformation, and only 2 are in the extended conformation. The packing of the VH and VL domains is consistent with our knowledge of antibody structure, and the tilt angles between these domains cover a range of 11 degrees. Two of 16 structures showed particularly large variations in the tilt angles when compared with the other pairings. The structures and their analyses provide a rich foundation for future antibody modeling and engineering efforts.     

秧宝灵防止早稻烂秧的生理基础

秧宝灵浸渍早稻种子,可有效地防止其烂秧发生和提高秧苗素质。这主要是由于秧宝灵处理后能加快幼叶的转绿速度,增加芽和幼叶的束缚水含量,提高芽的可溶性蛋白质含量,增强幼苗根系的活力,从而使秧苗具有较强的抗低温胁迫的能力。     

全国高等师范院校植物地理学研究讨论会在穗召开

全国高等师范院校“植物地理学”研究讨论会于1982年10月20日在广州开幕,11月7日在湛江胜利闭幕。出席会议的除全国31所高师地理系44位代表外;还邀请了部分综合性大学、中国科学院北京、长春地理研究所的专家、教授以及有关专业的编辑部代表8人,     

Exploration of ring size in a series of cyclic vicinal diamines with σ(1) receptor affinity

Imidazolidine and 1,4-diazepane analogs of N-(2-benzofuranyl)methyl-N'-(4-alkoxybenzyl)piperazines were prepared to explore the effect of ring contraction and expansion on σ receptor affinity and subtype selectivity within a series of cyclic diamines. In vitro receptor binding assays revealed that all cyclic vicinal diamines possessed affinity and selectivity for σ(1) receptors. The imidazolidines possessed nanomolar σ(1) affinities (K(i)=6.45-53.5nM), and relatively low levels of subtype selectivity (σ(2)/σ(1)=58-237). However, the piperazines and diazepanes achieved picomolar σ(1) interactions, with K(i) ranges of 0.05-10.28 and 0.10-0.194nM, respectively. Moreover, the piperazines and diazepanes showed excellent discrimination over the σ(2) receptor, with σ(1) selectivities of 143-16140 and 220-11542, respectively.