A general method for chimerization of monoclonal antibodies by inverse polymerase chain reaction which conserves authentic N-terminal sequences.

Chimerization of antibodies (Ab) by cloning the V (variable) regions encoding the light and heavy chains with degenerate oligodeoxyribonucleotide primers matching to framework region 1 and to the joining regions, leads to Ab with altered amino acids at the N-terminus compared to those of the parental Ab. This is due to N-terminal framework 1 sequences in the expression vectors [Larrick et al., Bio/Technology 7 (1989) 937-938; Le Boeuf et al., Gene (1989) 371-377; Orlandi et al., Proc. Natl. Acad. Sci. USA 86 (1989) 3833-3837]. This might lead to Ab with altered affinity to the antigen due to interaction of framework sequences with complementarity determining regions. Moreover, some V regions may be refractory to cloning by this procedure. Here, we describe a method to circumvent these potential problems. The V regions for both chains of the Ab are cloned by inverse polymerase chain reaction (PCR) with primers matching the known constant region sequences of the Ab. After sequencing, PCR fragments corresponding to the V regions of both chains are inserted in-frame into appropriate expression vectors leading to Ab with unaltered N-terminal sequences after expression in mammalian cells. The procedure is illustrated with an Ab directed against the beta chain of the human interleukin-2 receptor.     

Micropipette suction for measuring piconewton forces of adhesion and tether formation from neutrophil membranes.

A new method for measuring piconewton-scale forces that employs micropipette suction is presented here. Spherical cells or beads are used directly as force transducers, and forces as small as 10-20 pN can be imposed. When the transducer is stationary in the pipette, the force is simply the product of the suction pressure and the cross-sectional area of the pipette minus a small correction for the narrow gap that exists between the transducer and the pipette wall. When the transducer is moving along the pipette, the force on it is corrected by a factor that is proportional to the ratio of its velocity relative to its drag-free velocity. With this technique, the minimum force required to form a membrane tether from neutrophils is determined (45 pN), and the length of the microvilli on the surface of neutrophils is inferred. The strength of this technique is in its simplicity and its ability to measure forces between cells without requiring a separate theory or a calibration against an external standard and without requiring the use of a solid surface.     

红毛五加叶的三萜皂甙

红毛五加（ＡｃａｎｔｈｏｐａｎａｘｇｉｒａｌｄｉｉＨａｒｍｓ）系五加科五加属植物,分布于河北、河南、四川、陕西、甘肃等省,有祛风湿、通关节、强筋骨、治痿痹等功效［１］。其化学成分未见报道。本文报道红毛五加叶的５个三萜皂甙（甙Ⅰ、Ⅱ、Ⅲ、Ⅳ和Ⅴ）的分离鉴定。它们均首次从该属植物发现,其结构如下：　　　　　　　　　　　　　Ｒ１　　　　　　　　　　　　　　Ｒ２　　　　　　　　Ⅰ　ｒｈａｍ－（１→２）－ａｒａ　　　　　Ｈ　　　　　　　Ⅱ　Ｈ　　　ｒｈａｍ－（１→４）－ｇｌｃ－（１→６）－ｇｌｃ　　　　　…     

番茄种子经激光和咖啡因处理后其当代生物效应的研究

咖啡因具有抑制一些酶的活性,可减弱或消除生物体自身对激光引起的生物效应的修复作用。试验证明咖啡因对番茄种子萌发有强烈的抑制作用,咖啡因和激光复合处理生物效应显著,可降低番茄种子的发芽,并促进番茄果实增大和生长前期速率加快。     

胶质母细胞瘤外泌体的作用机制研究进展

胶质母细胞瘤(glioblastoma,GBM)因组织学异质性、侵袭能力强、术后复发快等问题,致使患者经手术治疗、化疗和放疗后的预后差,总体生存期短。GBM细胞来源外泌体(GBM cell-derived exosome,GBM-exo)能够通过其携带的细胞因子、miRNA、DNA和蛋白质等调节GBM细胞的增殖和迁移,通过血管生成蛋白和非编码RNA促进肿瘤血管生成,通过调节因子、蛋白质和药物靶向免疫检查点等介导肿瘤免疫逃逸,以及通过非编码RNA对抗GBM细胞的耐药性,有望成为个性化治疗GBM的重要靶标,且可以作为GBM的诊断和预后标志物。本文阐述了GBM-exo的制备方法和生物学特征,及其在GBM细胞增殖、血管生成、免疫逃逸和耐药性方面的作用和分子机制,为研发诊治GBM的新策略提供参考。     

(Zn·Cd)S:Ag-KI催化的光合磷酸化

以半导体材料(Zn·Cd)S:Ag-KI为催化剂,在普通卤钨灯光照射下,成功地模拟了光合作用的光合磷酸化.文章报导了光强、照光时间、ADP浓度、Pi浓度及催化剂量等对ATP合成的影响.在合适的条件下,ADP浓度为1×10~(-3)mmolL时转化率可达到4-6°.最后有一简单讨论.     

柳牡蛎蚧生命表的研究

1 引言 柳牡蛎蚧(Lepidosaphes salicina Bersch)(同翅目:盾蚧科)是一种以为害杨树为主的刺吸式害虫之一,广泛分布于“三北”防护林区,该蚧一年发生一代,以卵越冬。通过刺吸式口器刺入树皮内,吸取树木养分和水分,并使树木表皮栓化。同时,由于枝干被蚧壳所覆盖,对呼吸及光合作用也有影响,特别是幼树被害后,一般