Protein molecule, interactions with surfaces

All these alterations, which may be induced when a protein molecule interacts with a membrane surface either during convective (filtration) processes or under diffusive... 

In interpreting adsorption isotherms, a distinction should be made between very low coverage (initial part of the isotherm), where the protein molecules interact with the sorbent surface only, and high surface coverage (adsorption plateau), where lateral interactions between the adsorbed molecules play a role as well. 

All of these alterations, which may be induced when a protein molecule interacts with a membrane surface either during convective (filtration) processes or under diffusive conditions, can be reported by intrinsic fluorescence probes such as tryptophan residues and detected by using appropriate fluorescence techniques. In fact, the use of these techniques and the correct interpretation of their response is only possible when the number of tryptophan residues present in the protein is relatively low (one or two) because, otherwise, it becomes extremely difficult to assign a given fluorescence response to the corresponding tryptophan, limiting the interpretation effort. 

Capture array involves the immobilization of non-protein molecules onto the surface which can interact with proteins in the solute phase. Generally, capture molecules may be broad capture agents based on chromatography type surface chemistries such as ion exchange, hydrophobic and metal affinity functionality, or they may be highly specific such as molecular imprinted polymers or oligonucleotide aptamers. 

Protein molecules have a high propensity to interact with surfaces, making them susceptible to adsorption and denaturation at air-liquid, vial-liquid, and liquid-liquid... 

Some ligands do not interact principally with cell surface receptors, but diffuse into cells and bind to intracellular receptors in the cytoplasm. For example, ligand binding to cytoplasmic steroid receptors initiates a process that is not well understood but that involves the movement of steroid-bound receptor into the cell nucleus, where the receptor molecule interacts with genomic material, resulting in alterations in gene expression and protein synthesis. 

The distinction between substrate binding and supersubstrate binding as it has developed from studies on lipolytic enzymes has far-reaching implications. Many of the substrates of interacellular metabolism are partially immobilized, i.e., they are parts of biological membranes. The enzymes acting on such substrates are much larger than the substrate molecules, and the reactive center of the enzyme occupies only a small part of the surface of the enzymic protein. The rest of the protein must interact with the environment and in particular with the matrix in which... 

Most transducer proteins that interact with cell-surface receptors are GTP-binding proteins, commonly called G proteins. G proteins typically are composed of three subunits (x, P, and y. When the receptor is in the unbound state, aU three subunits are bound together to form a heterotrimer that is in close association with the membrane-bound receptor. In this state, GDP is bound to the a-subunit (Figure 7-2). Binding of the hormone by the receptor causes a conformational change such that the a-subunit is able to exchange the bound GDP for a molecule of GTP. The GTP-bound a-subunit separates from the Py-dimer and is able to interact with the effector enzyme in either a stimulatory or inhibitory manner, depending on the nature of the a-subunit. Some... 

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