Cooperative Noncovalent Interactions Research Articles

Noncovalent Cross-links in Context with Other Structural and Functional Elements of Proteins

Proteins are heteropolymers with evolutionary selected native sequences of residues. These native sequences code for unique and stable 3D structures indispensable for biochemical activity and for proteolysis resistance, the latter which guarantees an appropriate lifetime for the protein in the protease rich cellular environment. Cross-links between residues close in space but far in the primary structure are required to maintain the folded structure of proteins. Some of these cross-links are covalent, most frequently disulfide bonds, but the majority of the cross-links are sets of cooperative noncovalent long-range interactions. In this paper we focus on special clusters of noncovalent long-range interactions: the Stabilization Centers (SCs). The relation between the SCs and secondary structural elements as well as the relation between SCs and functionally important regions of proteins are presented to show a detailed picture of these clusters, which are believed to be primarily responsible for major aspects of protein stability.

Self-Assembly of Discrete Organometallic−Organic Hybrid Supramolecular Arrays from Ferrocenyl Dipyridines and Terephthalic and Trimesic Acids

Reactions of ferrocenyl dipyridines (1a,b) with terephthalic (2) and trimesic acid (4) form [2+2] and [3+2] supramolecular assemblies 3 and 5, respectively. Crystallographic analyses reveal that they are stabilized by cooperative noncovalent interactions involving multiple hydrogen-bonding and π−π interactions.

On recognition phenomena in polymer–minute particle interactions and pseudo-matrix processes

Equations describing equilibria in noncovalent interactions between macromolecules and minute particles were obtained by appropriate modification of theoretical dependences derived previously by statistico-thermodynamical treatment of cooperative noncovalent interactions between long (‘polymer’) and relatively short (‘oligomer’) macromolecules (the term ‘minute’ means that a macromolecule is long enough to cover the surface of more than one particle). The equations predict exponential dependence of polymer–minute particle complexes stability on the particle's surface area, and high selectivity (‘recognition’ phenomena) of the interactions with regard to the size of the particles and structure of both particles and macromolecules. Based on the equations, growth process of a particle in solution of appropriate polymer (termed ‘pseudo-matrix’) was treated theoretically in assumption that mutual recognition (i.e. complexation) of the particle and a macromolecule brings the growth to a stop (the term ‘pseudo-matrix processes’ was proposed recently to define such a processes). It was shown that: (a) at very weak noncovalent polymer–particle interactions, the size of ‘dead’ particles should correspond to ∼1–10 nm in diameter; (b) the size should depend on the interaction energy, temperature, and pseudo-matrix concentration; (c) size distribution of the particles must be very narrow; and (d) in simultaneous presence of two or more macromolecular pseudo-matrices, the size control must be effectuated by that one which is capable to recognize the particles on the earliest stage of their growth. The correspondence of the predictions to experimental data and possible methods of particles’ size control in pseudo-matrix processes are discussed.