Noncovalent interaction

DIPHTHERIA TOXIN DIPOLAR BOND DIPOLE-DIPOLE INTERACTION NONCOVALENT INTERACTLONS Dipole-dipole resonance energy transfer, FLUORESCENCE... 

Dipole-induced dipole interactions, NONCOVALENT INTERACTIONS DIPOLE MOMENT Diradical,... 

FIGURE 16-10 Iron-sulfur center in aconitase. The iron-sulfur center is in red, the citrate molecule in blue. Three Cys residues of the enzyme bind three iron atoms the fourth iron is bound to one of the carboxyl groups of citrate and also interacts noncovalently with a hydroxyl group of citrate (dashed bond). A basic residue ( B) on the enzyme helps to position the citrate in the active site. The iron-sulfur center acts in both substrate binding and catalysis. The general properties of iron-sulfur proteins are discussed in Chapter 19 (see Fig. 19-5). 

Antibodies interact noncovalently with their target epitope, and the strength of this interaction is characterized by the kinetics of association and dissociation of the antibody. Antibody-antigen interactions are in principle reversible, and appropriate conditions must therefore be selected for a given antibody to bind with reproducible stoichiometry to its target antigen. Linkage of the antibody to an appropriate fluorochrome will mean that the number of antibody molecules bound will be reflected by the fluorescence intensity/cell. 

The active sites of proteinases not only contain the catalytic site but also specific binding sites on the enzyme surface, which interact noncovalently with individual amino add residues of the polypeptide substrate, The peptide bond hvdrolvzed bv the nroteinase is called the sdssile or Ihe Pl-Pl bond... 

High hydrostatic pressure induces changes in protein conformation, solvation and enzyme activities via reversible and non-reversible effects on intra- and inter-molecular interactions (noncovalent bonds) [1]. To have access to these structural modifications, spectroscopic investigations are required which necessitate special spectroscopic adaptations. Two improvements are presented first for enzyme reactions and second for structural determination. 

Noncovalent interactions are central to many key biological functions. The self-assembly of the plasma and organelle membranes, association between receptors and ligands, and folding of RNA and protein molecules are all controlled by noncovalent interactions. Noncovalent forces in the design of proteins have proved useful in gaining insight into... 

Figure 3.88 (a) Possible modes of a polymer interacting noncovalently with carbon... 

Unesterified fatty acids within cells are commonly bound by fatty acid-binding proteins (FABPs), which belong to a group of small cytosolic proteins that facilitate the Intracellular movement of many lipids. These proteins contain a hydrophobic pocket lined by p sheets (Figure 18-3). A long-chain fatty acid can fit into this pocket and Interact noncovalently with the surrounding protein. 

Many types of forces and interactions play a role in holding a protein together in its correct, native conformation. Some of these forces are covalent, but many are not. The primary structure of a protein—the order of amino acids in the polypeptide chain—depends on the formation of peptide bonds, which are covalent. Higher-order levels of structure, such as the conformation of the backbone (secondary structure) and the positions of all the atoms in the protein (tertiary structure), depend on noncovalent interactions. If the protein consists of several subunits, the interaction of the subunits (quaternary structure. Section 4.5) also depends on noncovalent interactions. Noncovalent stabilizing forces contribute to the most stable structure for a given protein, the one with the lowest energy. 

Li et al. [48] described a virtual screen on the SPECS database to identify inhibitors for the cysteine protease falcipain-2 as promising target for malaria treatment. Based on the available X-ray structure of falcipain-2, two different docking protocols based on Glide [47] and GAsDock [49] were employed to identify 28 nonpeptidic inhibitors. The best compound exhibited an IC50 value of 2.4 pM (Figure 12.2b). Further biochemical evaluations showed that the best inhibitor interacts noncovalently with the active site of this cysteine protease. 

The binding reaction between a biopolymer (ligate) and a molecular counterpart (ligand) results from the sum of various types of interactions. Noncovalent interactions such as van der Waals and electrostatic interactions, hydrogen bonding, and the size and shape of the molecules contribute to molecular... 

It is not surprising that the development of synthetic molecules which can interact noncovalently with biological... 

The other approach to supramolecular assembly of CNTs entails endohedral functionalization, where molecules interact noncovalently with the inside wall of the CNT (Figure 1). CNTs have been endohedrally functionalized by various materials including Ceo fullerenes, liquid lead, metal oxides, manganese, " and water. ... 

Some aromatic molecules, such as pyrene, porphyrin, and their derivatives, have strong affinity with the basal plan of graphene sheets via n-n interactions. Noncovalent functionalization has been used in the functionalization of CNTs, and as the rise of graphene, it has been used for functionalization of graphene. 

The heart of any enantioseparation by liquid chromatography is a chiral column packed with a CSP or rarely a chiral selector immobilized on the wall of a capillary. A CSP consists of a chiral selector and an inert carrier. Both constituents are equally important for the separation performance. The chromatographic literature reports several himdreds of chiral compoimds applied as chiral LC selectors. A more or less complete overview of all materials applied as chiral selectors is impossible within the framework of this short chapter. In principle, any chiral compound possessing the ability to interact noncovalently with chiral molecules has the potential to be used as chiral selector in liquid chromatography. A chiral selector has to meet a set of characteristics that depend on the goal of the separation as well as the mode and technique used. The advantages and bottlenecks of the major classes of commercially available CSPs are summarized in Table 4.1. 

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