MOLECULAR BASIS OF ANTIGENIC SPECIFICITY

高亲和力单克隆抗体的热力学初步研究 抗荧光抗体（4-4-20）表明其活性位点是一个 浅疏水口袋，主要通过 熵 此外，高分辨率衍射数据（2.5埃）是 可用于该抗体的配体化抗原结合片段（Fab）， 其在16%聚乙二醇中结晶。 配体Fab片段还 在极性较小的溶剂体系中结晶（46.7%）， 2-甲基-2，4-戊二醇）。 完整IgG分子的亲和力为 300-在这种溶剂中会降低一倍 相关晶体和溶液研究 两个水晶系统都在计划中。 我们希望通过这些信息来解释 抗原与抗体结合的分子基础 结晶 目前正在进行其他四种单克隆抗荧光素抗体的试验。 与4-4-20独特相关的抗体，但表现出 其亲和力在1000倍范围内变化。 计划进行解决方案研究 来确定熵优势和活性位点 4-4-20的特征对于其它克隆也是共同的。 独特型决定因素通常被认为位于或接近 活性部位 晶体研究应阐明独特型的性质 决定因素和独特型试剂是否是有效的工具， 相关的活跃网站 高分辨率衍射数据（2.0埃）可用于 单克隆抗体的未配体Fab片段，其结合单个 链DNA（BV 04 -01）。 在溶液中，该蛋白质显示出一种碱， 对嘧啶的特异性，对胸腺嘧啶的亲和力大于 尿嘧啶。 这种抗体具有临床重要性，因为它是分离出来的， 来自一只患有类似系统性狼疮的自身免疫综合征的老鼠 红斑 我们已经获得了低分辨率（6埃）结构 并计划将此解决方案扩展到更高分辨率。 我们还计划 将寡核苷酸灌注到晶体中以确定 观察到的嘧啶特异性。

Preliminary thermodynamic studies of a high affinity monoclonal anti-fluorescyl antibody (4-4-20) indicate that its active site is a shallow hydrophobic pocket, which binds fluorescein primarily through entropy. Moreover, high resolution diffraction data (2.5 Angstrom) is available for the liganded antigen binding fragment (Fab) of this antibody, which crystallizes in 16% polyethyleneglycol. Liganded Fab fragments also crystallize in a less polar solvent system (46.7% 2-methyl-2,4-pentanediol). The affinity of the intact IgG molecule is 300-fold lower in this solvent. Correlated crystal and solution studies of both crystal systems are planned. With this information we hope to explain the molecular basis of antigen binding to this antibody. Crystallization trials are currently in progress with four other monoclonal anti-fluorescyl antibodies which are idiotypically related to 4-4-20, but exhibit affinities which vary over a 1000-fold range. Solution studies are planned to determine whether the entropy predominance and active site characteristics of 4-4-20 are common to the other clones as well. Idiotypic determinants are generally thought to be located at or near the active site. Crystal studies should clarify the nature of idiotypic determinants and whether idiotypic reagents are valid tools for identifying related active sites. High resolution diffraction data (2.0 Angstrom) is available for the unliganded Fab fragment of a monoclonal antibody which binds single stranded DNA (BV04-01). In solution, the protein exhibited a base specificity for pyrimidines, with greater affinity for thymine than uracil. This antibody is of clinical importance because it was isolated from a mouse with an autoimmune syndrome similar to systemic lupus erythematosus. We have obtained a low-resolution (6 Angstrom) structure and plan to extend this solution to higher resolution. We also plan to perfuse oligonucleotides into crystals to determine the molecular basis of the observed pyrimidine specificity.