Gold nanoparticles are new kinds of nanomaterials. Their large surface-to-volume ratio, stability, excellent biocompatibility, low toxicity and functionality make them very attractive for biomedical applications. Therefore we have analyzed how dendronized gold nanoparticles interact with human alpha-1-microglobulin. This is a glycoprotein of ∼30kDa present in blood plasma and some tissues of the human body. Comparing 3 nanoparticles with different dendronization, we conclude that the effect of a nanoparticle on the structure of alpha-1-microglobulin significantly decreased with second and third generations dendrons as a result of less exposure of the metal cores in the nanoparticles. These interactions indicate weak changes in the immunochemical properties of the protein, whereas the dendron coating had no effect. Thus, dendronization of gold nanoparticles helps to modify their binding properties by shielding them from interactions with plasma proteins.

Functionalization of gold nanoparticles by different chemical groups is an important issue regarding the biomedical applications of such particles. Therefore we have analyzed the interaction between gold nanoparticles functionalized by carbosilane dendrons with human serum albumin at different pHs, and in the presence of the protein unfolding agent, guanidine hydrochloride, using circular dichroism, zeta-potential and fluorescence quenching. The effect of a nanoparticle dendronization and pure dendrons on the immunoreactivity of albumin was estimated using ELISA. In addition, the tool to estimate the binding capacity of dendronized gold nanoparticles using a hydrophobic fluorescent probe 1,8-ANS (1-anilinonaphthalene-8-sulfonic acid) was chosen. We concluded that the effect of a nanoparticle on the structure, immunochemical properties and unfolding of albumin significantly decreased with second and third generations dendrons attached. Differences in pH dependence of the interaction between nanoparticles, their dendrons and albumin showed several effects of the "dendritic corona" and the metallic part of nanoparticle on the protein. These interactions indicate changes in the immunoreactivity of the protein, whereas dendron coating per se had no effect. Thus, dendronization of gold nanoparticles helps to shield them from interactions with plasma proteins.

We have used fluorescence spectroscopy methods to show that imidacloprid and its structural analogs form complexes with human serum albumin (HSA). The nature of the spectral changes in the ligand×protein systems and the calculated complexation parameters suggest that these low molecular weight compounds mainly bind to a specific section of the protein molecule, near the tryptophan residue in the 214 position of the polypeptide chain. We have found that the association constants are on the order of 10 4 M -1 , and the affinity of the ligands for HSA varies in the series 6-chloronicotinic acid > 6-methoxynicotinic acid = imidacloprid > the keto analog of imidacloprid. The major contribution to the complexation energy probably comes from hydrophobic interaction forces with participation of the aromatic pyridine ring of the ligands, while additional enhancement of ligand-protein affinity can be provided by the nitroimine group of imidacloprid.Key words: human serum albumin, neonicotinoid, imidacloprid, quenching of fluorescence, ligand-protein binding.Introduction. Neonicotinoids are a new and very important class of insecticides with selective action which are increasingly aggressively displacing pyrethroids, organophosphorus compounds, and methylcarbamates from the area of application for protection of plants from insect pests. The selectivity of action of neonicotinoids is determined by the properties of their molecular target: the nicotinic acetylcholine receptor. These pesticides have high affinity for the insect receptor and bind weakly to other types of receptors, in particular exhibiting low toxicity for mammals [1,2]. The molecular aspects of high affinity and selectivity for binding of neonicotinoids and their analogs by receptor proteins and the physicochemical nature of the interactions in the complexes formed have been studied in many papers. As a result, some structural elements and also chemical groups have been identified in the insecticides and the receptor that are involved in complexation, and computer models of the ligand×protein interaction have been proposed based on a quantum chemical method [1,[3][4][5][6].Another important direction in studies of the biological properties of pesticides is directly related to protection of the health of humans and agricultural animals, and includes study of the interactions between these xenobiotics and proteins, enzymes, and receptors in blood plasma and tissues. The chemical structure of many pesticides, including insecticides in the neonicotinoid class, contains sections and groups capable of forming electrostatic, hydrophobic, and hydrogen bonds as well as other types of bonds typical of endogenous ligands in their complexes with proteins. Therefore many pesticides can play the role of exogenous ligands and alter their own properties within the composition of protein complexes, as is true for natural bioregulators such as hormones. These changes can involve metabolic parameters and biological effects of the pesticides in the human body and in the bodies of...

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