Protein surface hydrophobicity

The method of Kato and Nakai (27) for determining protein surface hydrophobicity was adapted for evaluating procyanidin binding to BSA and Gl. The procedure is based on the fact that the fluorescence quantum yield of cis-parinaric acid increases 40-fold when cis-parinaric acid enters a hydrophobic environment from a hydrophilic environment. The digestion of BSA by trypsin in the presence of procyanidin dimer, procyanidin trimer and black bean procyanidin polymer was evaluated by discontinuous sodium dodecyl sulfate (SDS) slab gel electrophoresis and a picryl sulfonic acid (TNBS) assay (28). 

Initial screening conditions are suggested in Table 6.1. Multiple pH values are included because mobile-phase pH can significantly affect retention. Major selectivity shifts such as transpositions in elution order are fairly common changes in resolution are much more so.2,14-16 Changes in retention due to pH variation relate to protein hydration. Proteins are minimally charged at their isoelectric points (pis). This means that they carry the minimum of electrostricted hydration water. Both protein surface hydrophobicity and HIC retention should therefore reach their maximum at a protein s pi.6 As pH is either increased or... 

Boatright and Hettiarachchy (1995) reported that solubility improvement in soy protein resulted from preventing its oxidation by adding antioxidants and corresponded with the increase in total protein surface hydrophobicity as determined by the SDS binding method (see Basic Protocol 2). This hydrophobicity was not the total protein hydrophobicity but is similar to the exposable hydrophobicity, Se, which is Sq measured in the presence of SDS (Townsend and Nakai, 1983). This change in the exposure of hydrophobic sites in protein molecules is dependent on the concentration of SDS used in the analysis. One of the advantages of the SDS binding method is that there is no need for an expensive spectrofluorometer. 

Arteaga, G.E. 1994. Assessment of protein surface hydrophobicity by spectroscopic methods and its relation to emulsifying properties of proteins. Ph.D. Thesis, University of British Columbia, Vancouver, B.C., Canada. 

Chao, C.-C., Ma, Y.-S., and Stadtman, E.R. 1997. Modification of protein surface hydrophobicity and methionine oxidation by oxidative systems. Proc. Nail. Acad. Sci. U.S.A. 94 2969-2974. 

Figure 7 Correlation of plateau values with protein surface hydrophobicity (from hydrophobic interaction chromatography data) for the adsorption of egg-white lysozyme ( ), bovine pancrease ribonuclease (A), a-lact-albumin (x), sperm whale myoglobin ( ), and superoxide dismutase ( ) on negatively charged polystyrene in 50 mM KCI at 25°C and pH equal to pi of each protein. (From Ref. 17. Reprinted with permission.)...

Total internal reflection intrinsic fluorescence (TIRIF) spectroscopy and molecular graphics have been applied to study the adsorption behavior of two lysozymes on a set of three model surfaces. A recently devised TIRIF quantitation scheme was used to determine adsorption isotherms of both hen egg-white lysozyme (HEWL) and human milk lysozyme on the three model surfaces. This preliminary study suggests that the adsorption properties of the two lysozymes are significantly different, and that further comparative studies of the two lysozymes might prove to be beneficial in understanding how protein structure might influence adsorption properties. Molecular graphics was used to rationalize the adsorption results from TIRIF in terms of the proteins surface hydrophobic/hydrophillic character. 

M. Suzuki, J. Shigematsu, Y. Fukunishi, Y. Harada, and T. Yanagida, T. Komada, Coupling of Protein Surface Hydrophobicity Change to ATP Hydrolysis by Myosin Motor Domain. Biophys. J., 71,18-23,1997. 

Fig. 5.2. Loadings plot on the first two factors for 15 variables used to describe samples of meat and fish. SOL, solubility EC, emulsifying capacity DISP, dispersability FBC, fat binding capacity SH, sulphydryl content PROTEIN, protein content SEP, salt-extractable protein H20, moisture content pH, pH of a mince suspension FAT, crude fat content COOKLOSS, percentage weight lost after cooking GEL-M, gel strength of mince GEL-E, gel strength of extract ANS and CPA, protein surface hydrophobicity using aromatic (ANS) or aliphatic (CPA) fluorescent probe (from Li-Chan et at. 1987, with permission of the Institute of Food...

Arteaga, G.E. Li-Chan, E. Nakai, S. Assessment of protein surface hydrophobicity by proton nuclear magnetic resonance spectroscopy. Poster 68A-39, presented at Annual Meeting, Institute of Food Technologists, Anaheim, CA, June 3—7, 1995. 

Proteins may bind a variety of hydrophobic molecules or flavor compounds because protein molecules possess a number of hydrophobic sites on their surfaces (i.e., protein surface hydrophobicity, PSH). Proteins such as bovine serum albumin (Beyeler and Solms, 1974 Cardamone and Puri, 1992 Fujii et al., 1992 Richieri et al., 1993), soy proteins (Beyeler and Solms, 1974 Petruccelli and Anon, 1994) and b-lactoglobulin (Akita and Nakai, 1980) are known for their binding properties or hydrophobic traits. Because... 

Figure 1. Effect of peanut maturity on protein surface hydrophobicity (PSH). Ye = yellow Or = orange Br = brown and B1 = black. Each data point is the mean of three determinations (n=3).

Hydrophobicity Adsorption of proteins from the aqueous solution to hydrophobic interfaces is considered mainly to be entropically driven [38,65]. A direct correlation between protein surface hydrophobicity and its adsorption to hydro-phobic interfaces has been shown for the studies conducted at solid-liquid [38, 66] and liquid-liquid interfaces [67]. 

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