Gold-protein interactions

Covalent attachment of enzymes to surfaces is often intuitively perceived as being more reliable than direct adsorption, but multisite physical interactions can in fact yield a comparably strong and stable union, as demonstrated by several biological examples. The biotin/streptavidin interaction requires a force of about 0.3 nN to be severed [Lee et al., 2007], and protein/protein interactions typically require 0.1 nN to break, but values over 1 nN have also been reported [Weisel et al., 2003]. These forces are comparable to those required to mpture weaker chemical bonds such as the gold-thiolate bond (1 nN for an alkanethiol, and even only 0.3 nN for a 1,3-aUcanedithiol [Langry et al., 2005]) and the poly(His)-Ni(NTA) bond (0.24 nN, [Levy and Maaloum, 2005]). 

The innate sensitivity of DNA-mediated CT to perturbations in the TT-stack has prompted us to employ this chemistry as a probe of stacking structure and dynamics. We have developed a new class of DNA-based diagnostic tools that diagnose DNA mutations such as single base-pair mismatches and lesions, analyze DNA-protein interactions, and probe the sequence-depen-dent dynamics and flexibility of DNA. These applications rely on electrochemical probing of CT in DNA films self-assembled on gold electrodes. 

For a complete functional study of a biological pathway, it is often necessary to confirm the important protein interactions by in vivo experiments. This can be done by demonstrating protein localizations on a microscopic level, for instance, by tagging proteins with the green fluorescent protein or localizing them with antibodies and colloidal gold particles using an electron microscope. Additional, very specific biochemical experiments are often required to confirm the putative protein function. 

Some elements found in hody tissues have no apparent physiological role, hut have not been shown in he toxic. Examples arc rubidium, strontium, titanium, niobium, germanium, and lanthanum. Other elements are toxic when found in greater than trace amounts, and sometimes in trace amounts. These taller elements include arsenic, mercury, lead, cadmium, silver, zirconium, beryllium, and thallium. Numerous irlhcr elements are used in medicine in non-nulrieni roles. These include lithium, bismuth, antimony, bromine, platinum, and gold. The interactions of mineral nutrients with carbohydrates, fats, and proteins, minerals with vitamins (qv). and mineral nutrients with toxic elements are areas of active investigation. 

Fig. 2.5 (a) An aptamer-target protein interaction (adapted from Tuerk and Gold 1990, p. 505). (b) Principle of the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) process (adapted from Tombelli et al., 2005, p. 2424)... 

First mention of gold-protein complexing and interaction with light. 

Hardcastle IR, Ahmed SU, Atkins H, Eamie G, Golding BT, Griffin RJ, Guyenne S, Hutton C, Kallblad P, Kemp SJ, Kitch-ing MS, Newell DR, Norbedo S, Northen JS, Reid RJ, Sara-vanan K, Willems HM, Lunec J. Small-molecule inhibitors of the MDM2-p53 protein-protein interaction based on an isoindolinone scaffold. J. Med. Chem. 2006 49 6209-6221. 

To understand the structural requirements for a molecule to promote cytochrome c electrochemistry at gold electrodes, over 50 bifunctional organic compounds (X Y, where X is a surface-active functional group, Y is the protein-interactive ftmctionality, and is the linking structure) were investigated (21) to assess their ability to promote cytochrome c electrochemistry at a gold electrode. The results can be summarized as follows ... 

Apart from the presence of proteins, several other factors can influence NM behavior in culture media, including the salt composition, the pH, or the buffer capacity. Using gold nanoparticles (AuNP) of three sizes Maiorano et al. [24] demonstrated that the nanoparticle-protein interactions are differendy mediated when AuNP are suspended in two common cell culture media (DMEM and RPMI) supplemented with fetal bovine serum. An increased protein coating and different size distribution were observed in AuNP suspended in DMEM in comparison to RPMI. Most impor-tantiy, differences were also found in the biological responses of two cell lines (HeLa and U937), as the intracellular internalization and cytotoxicity were higher in cells exposed to AuNP in RPMI, where the protein corona was less abundant. 

Gold nanoparticles are widely used for protein immobilization, due to the intrinsic property of the gold to interact with proteins. The protein molecules can be directly attached on the gold nanoparticles surface, which renders gold nanoparticles one of the most biocompatible nanomaterials. Numerous works have been published on this field the last years [173-175],... 

Connective tissue diseases can result in protein denaturation whose degradation may be antigenic and causative of RA s inflammation. Gold compounds, interacting with such proteins, may help stabilize them. A protective ability of gold thiomalate toward heat-caused gammaglobulin aggregation can be demonstrated. 

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