Biophysics of Macromolecular Complexes

染色质结构和架构。 细胞核内的DNA被包装成染色质，目前有多种模型描述了被认为存在于体内的浓缩的30 nm染色质纤维的结构。 我们特别感兴趣的是了解凝聚染色质内的DNA组织，以及由组织蛋白质（如CTCF）对高阶组织施加的拓扑约束。 因此，我们正在开发利用体外模型系统和天然染色质片段的高分辨率染色体捕获构象测定，例如先前研究的两侧为发育调节的叶酸受体和β-珠蛋白基因的浓缩异染色质。 这些研究将使我们能够更好地了解体内30 nm染色质纤维的结构，从而深入了解染色质结构与基因表达和DNA复制等基本过程之间的关系。 大分子组装体。 在与分子生物学实验室的成员和其他人的合作中，蛋白质和蛋白质-核酸组装体已经使用流体动力学方法在它们的形状、化学计量和相互作用亲和力方面进行了表征。 这些研究补充了目前的生物化学，结构和生理学研究。 在最近发表的与Appella博士合作进行的工作中提供了一个例子，其中我们表征了用于组装多价整联蛋白拮抗剂的肽核酸纳米支架。 具体来说，我们发现用整联蛋白拮抗剂修饰的5个12个碱基的肽核酸（PNA）与60个碱基的互补单链DNA形成了稳定的复合物。 以这种方式，我们不仅验证了用于设计可编程多价展示的合成策略，而且证实了复合物的稳定性（Englund等人，2012年）。

Chromatin structure and architecture. DNA within the cell nucleus is packaged into chromatin and a variety of models presently describe the structure of the condensed 30 nm chromatin fiber thought to exist in vivo. We are specifically interested in understanding the organization of DNA within condensed chromatin, as well as the topological constraints imposed on the higher order organization imposed by organizing proteins such as CTCF. Accordingly, we are developing high resolution chromosome capture conformation assays utilizing in vitro model systems and native chromatin fragments, such as the previously studied condensed heterochromatin flanked by the developmentally regulated folate receptor and beta-globin genes. These studies will allow us to better understand the structure of the 30 nm chromatin fiber in vivo, thus providing insight in the relations between chromatin structure and essential processes such as gene expression and DNA replication. Macromolecular assemblies. In collaboration with members of the Laboratory of Molecular Biology, and others, protein and protein-nucleic acid assemblies have been characterized in terms of their shape, stoichiometry and affinity of interaction using hydrodynamic methods. These studies complement current biochemical, structural and physiological investigations. An example is provided in recently published work carried out in collaboration with Dr. Appella where we characterized peptide nucleic acid nanoscaffolds used for the assembly of multivalent integrin antagonists. Specifically, we showed that five 12-base peptide nucleic acids (PNA) decorated with the integrin antagonist formed a stable complex with a 60-base complementary single stranded DNA. In this manner we have not only validated the synthetic strategy utilized for the design of programmable multivalent displays but also confirmed the stability of the complex (Englund et al., 2012).