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Contamination of total parenteral nutrition (TPN) fluids is a problem occurring when preparing admixtures of them. In the present study, we carried out an investigation into the cause of contamination with a view to its prevention. For the TPN admixtures prepared in our pharmacy, we investigated the number prepared, their contents, the number that had contaminants and the nature of the contaminating substances. Contaminants were found in about 10% of the TPN admixtures and micro-infrared spectrophotometer analysis indicated that most of the contaminants were pieces of the rubber produced by coring. Further, an investigation of a correlation between TPN prescription contents and the incidence of contamination showed that the highest incidence of contamination occurred in preparations made by a particular pharmaceutical company. In order to prevent rubber particles from being produced, we need to be very careful when sticking the needle into the rubber stopper during the mixing of TPN admixtures. However as it is difficult to prevent contamination completely, we suggest checking TPN admixtures for contamination after mixing them and using in-line filters when they are administered to patients.

Alpha(1)-acid glycoprotein (AGP) is a glycoprotein that consists of 183 amino acid residues and five carbohydrate chains and binds to neutral and basic drugs. We examined the structural properties and ligand-binding capacity of AGP in interactions with reverse micelles. Also, detailed information was obtained by comparing several different states of AGP. Interaction with reverse micelles induced a unique conformational transition (beta-sheet to alpha-helices) in AGP and decreased the binding capacity for the basic drug, chlorpromazine and the steroid hormone, progesterone to AGP. These structural conformations are very similar to those observed under conditions of acidity and high ionic strength (pH 2.0, 1.5 M NaCl). This structure seems to be an intermediate between the native state and the denatured state, possibly a molten globule. The present results suggest that when AGP interacts with the biomembrane, it undergoes a structural transition to a unique structure that differs from the native and denatured states and has a reduced ligand-binding capacity.

Human alpha(1)-acid glycoprotein (AGP), which is comprised of 183 amino acid residues and 5 carbohydrate chains, is a major plasma protein that binds to basic and neutral drugs as well as to steroid hormones. It has a beta-sheet-rich structure in aqueous solution. Our previous findings suggest that AGP forms an alpha-helix structure through an interaction with biomembranes. We report herein on a study of the mechanism of alpha-helix formation in AGP using various modified AGPs. The disulfide reduced AGP (R-AGP) was extensively unfolded, whereas asialylated AGP (A-AGP) maintained the native structure. Intriguingly, reduced and asialylated AGP (RA-AGP) increased the alpha-helix content as observed in the presence of biomembrane models, and showed a significant decrease in ligand binding capacity. This suggests that AGP has an innate tendency to form an alpha-helix structure, and disulfide bonds are a key factor in the conformational transition between the beta-sheet and alpha-helix structures. However, RA-AGP with all histidine residues chemically modified (HRA-AGP) was found to lose the intrinsic ability to form an alpha-helix structure. Furthermore, disulfide reduction of the H172A mutant expressed in Pichia pastoris also caused a similar loss of folding ability. The present results indicate that disulfide bonds and the C-terminal region, including H172 of AGP, play important roles in alpha-helix formation in the interaction of the protein with biomembranes.

Alpha1-acid glycoprotein (AGP) is a serum glycoprotein that mainly binds basic drugs. Previous reports have shown that AGP converts from a beta-sheet to an alpha-helix upon interaction with biomembranes. In the current studies, we found that alkanols, diols, and halogenols all induce this conformational change. Increased length and bulkiness of the hydrocarbon group and the presence of a halogen atom promoted this conversion, whereas the presence of a hydroxyl group inhibited it. Moreover, the effect was dependent on the hydrophobic and electrostatic properties of the alcohols. These results indicate that, in a membrane environment, hydrophobic and electrostatic factors cooperatively induce the transition of AGP from a beta-sheet to an alpha-helix.