PHYSICAL PRINCIPLES OF BIOMOLECULAR RECOGNITION, SELF-ASSEMBLY AND REGULATION

各种生物螺旋之间的相互作用控制蛋白质折叠和组装，DNA包装，蛋白质-DNA相互作用，结缔组织形成和稳定性，以及负责生物体中正常功能和病理学的许多其他过程。通过结合几种实验技术（紫外可见光谱、荧光光谱、红外光谱、X射线衍射、量热法等），在严谨的物理理论指导下，我们继续推进对这些最基本的分子识别反应的理解。在过去的一年中，我们最重要的成就是：（1）我们证明了I型胶原中的末端非螺旋肽在胶原纤维形成中起催化作用，而不是识别结构域。正确的分子识别所需的所有信息都编码在蛋白质的三螺旋结构域中。(2)我们测量了来自成骨细胞鼠（人III型成骨细胞的类似物）的小鼠的天然和重建胶原组织中的分子相互作用。相应的突变导致I型胶原同源三聚体的形成，其取代正常的异源三聚体。我们的研究表明，这些突变导致：（a）一些（仍未知）化合物的结合位点丢失，这些化合物充当稳定胶原纤维的分子胶;（B）负责胶原纤维形成和纤维稳定性的吸引力降低。(3)我们开始研究α 1（I）链中G349 C取代对I型胶原分子之间相互作用的影响。我们的初步数据表明，这种突变（在人类成骨细胞中很常见）本身没有显著的影响。观察到的表型表现和胶原-胶原相互作用的测量变化的主要来源似乎是由突变引起的翻译后蛋白质过度修饰。(4)我们发展了一个螺旋大分子在所有轴间角的静电相互作用的理论。这一理论解释了在DNA聚集体中观察到的双相行为的几个难题，包括宏观的相间距，双-双转变和扭曲感逆转。- 胶原，成骨细胞，DNA，光谱学，x射线衍射，理论

Interactions between various biological helices control protein folding and assembly, DNA packing, protein-DNA interactions, connective tissue formation and stability, and many other processes responsible for normal function and pathology in living organisms. By combining several experimental techniques (UV-VIS, fluorescence, and FTIR spectroscopy, x-ray diffraction, calorimetry, etc.) with rigorous physical theories, we continued to advance our understanding of these most basic molecular recognition reactions. Our most significant achievements during the past year were: (1) We demonstrated that terminal, non-helical peptides in type I collagen serve as catalytic rather than recognition domains in collagen fibrillogenesis. All information necessary for proper molecular recognition is encoded in the triple helical domain of the protein. (2) We measured molecular interactions in native and reconstituted collagen tissues from mice with osteogenesis imperfecta murine (an analogue of human type III osteogenesis imperfecta). The corresponding mutations lead to formation of type I collagen homotrimers that replace normal heterotrimers. Our studies suggest that these mutations lead to: (a) loss of binding sites for some (still unknown) compound that acts as a molecular glue stabilizing collagen fibers and (b) a reduction in the attractive force responsible for collagen fibrillogenesis and fiber stability. (3) We started investigation of the effect of G349C substitution in a1(I) chain on interaction between type I collagen molecules. Our preliminary data indicate that this mutation (common in human osteogenesis imperfecta) has nosignificant impact by itself. The main source of the observed phenotype manifestations and of the measured changes in collagen-collagen interactions appears to be post-translational protein overmodification, caused by the mutation. (4) We developed a theory of electrostatic interactions between helical macromolecules at all interaxial angles. This theory explains several puzzles of the observed cholesteric phase behavior in DNA aggregates, including the macroscopic pitch of the phase, the cholesteric- nematic transition, and twist sense reversal. - collagen, osteogenesis imperfecta, DNA, spectroscopy, x-ray diffraction, theory