TY - JOUR A1 - Kroll, Jürgen A1 - Rawel, Harshadrai Manilal A1 - Kröck, Regina T1 - Microwave digestion of proteins Y1 - 1998 ER - TY - JOUR A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen A1 - Schröder, Insa Sigrid T1 - In vitro enzymatic digestion of benzyl- and phenylisothiocyanate derivatized food proteins Y1 - 1998 ER - TY - JOUR A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen A1 - Riese-Schneider, Brigitte A1 - Haebel, Sophie T1 - Physicochemical and enzymatic properties of Benzyl-Isothiocyanate derivatized proteinases Y1 - 1998 ER - TY - JOUR A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen A1 - Riese-Schneider, Brigitte A1 - Haebel, Sophie T1 - Changes in physico-chemical and enzymatic properties of benzyl isothiocyanate derivatized proteinases Y1 - 1998 ER - TY - JOUR A1 - Rawel, Harshadrai Manilal A1 - Rohn, Sascha A1 - Kroll, Jürgen T1 - Reactions of selected secondary plant metabolites (glucosinolates and phenols) with food proteins and enzymes - Influence on physicochemical properties, enzyme activity and proteolytic dagradation Y1 - 2000 ER - TY - JOUR A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen A1 - Rohn, Sascha T1 - Reactions of phenol substances with lysozyme - physicochemical characterisation and proteolytic digestion of the derivatives Y1 - 2000 ER - TY - JOUR A1 - Kroll, Jürgen A1 - Rawel, Harshadrai Manilal A1 - Seidelmann, N. T1 - Physicochemical properties and susceptibility to proteolytic digestionof myoglobin-phenol derivatives Y1 - 2000 ER - TY - JOUR A1 - Kroll, Jürgen A1 - Rawel, Harshadrai Manilal T1 - Reactions of plant phenols with myoglobin : influence of chemical structure of the phenolic compounds Y1 - 2000 ER - TY - JOUR A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen A1 - Riese, B. T1 - Reaction of chlorogenic acid with lysozyme : physicochemical characterization and proteolytic digestion of the derivatives Y1 - 2000 ER - TY - JOUR A1 - Rohn, Sascha A1 - Rawel, Harshadrai Manilal A1 - Pietruschinski, Nadine A1 - Kroll, Jürgen T1 - In vitro inhibition of alpha -chymotryptic activity by phenolic compounds N2 - alpha-Chymotrypsin was modified by covalent attachment of selected phenolic and related compounds (caffeic acid, chlorogenic acid, ferulic acid, gallic acid, quinic acid, m-/o-/p-dihydroxybenzene and p-benzoquinone) at pH 9. The derivatives formed were characterised in terms of their activity and selected physicochemical properties. In vitro experiments showed that the proteolytic digestion of food proteins with alpha-chymotrypsin derivatives was adversely affected. This decrease depended on the reactivity of the phenolic and related substances tested as well as on the kind of substrate applied. The derivatisation was accompanied by a reduction in the amount of free lysine and tryptophan residues. Moreover, the solubility of the derivatives decreased over a broad pH range, with a parallel increase in the hydrophobicity. The isoelectric point was shifted to a lower pH value, and formation of high-molecular-weight fractions was documented by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Y1 - 2001 UR - http://www3.interscience.wiley.com/cgi-bin/abstract/86510624 ER - TY - JOUR A1 - Kroll, Jürgen A1 - Rawel, Harshadrai Manilal A1 - Rohn, Sascha A1 - Czajka, Dörte T1 - Interactions of glycinin with plant phenols : influence on chemical properties and proteolytic degradation of the proteins N2 - Soya glycinin was derivatized with different phenolic substances (caffeic-, chlorogenic-, gallic acid and quercetin). The protein derivatives formed have been characterized in terms of their properties where they showed changes in the content of free epsilon-amino groups, tryptophan and thiol groups. The derivatives have also been characterized in terms of their solubility at different pH-values to document the influence on the functional properties. Another objective of this paper was to demonstrate the influence on the digestibility of the proteins with one of the main enzymes of the gastro-intestinal tract (pancreatin) on the basis of in vitro experiments after derivatization with phenolic substances. The enzymatic digestion of the derivatized proteins was promoted. Y1 - 2001 UR - http://www3.interscience.wiley.com/cgi-bin/abstract/85513730 ER - TY - JOUR A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen A1 - Hohl, U. C. T1 - Model studies on reactions of plant phenols with whey proteins Y1 - 2001 ER - TY - JOUR A1 - Kroll, Jürgen A1 - Rawel, Harshadrai Manilal T1 - Reactions of plant phenols with myoglobin : influence of chemical structure of the phenolic compounds Y1 - 2001 ER - TY - JOUR A1 - Rawel, Harshadrai Manilal A1 - Czajka, Dörte A1 - Rohn, Sascha A1 - Kroll, Jürgen T1 - Interactions of different phenolic acids and flavonoids with soy proteins N2 - Soy glycinin (SG) and soy trypsin inhibitor (STI) were derivatized by chlorogenic- and caffeic acid (cinnamic acids, C6 - C3 - structure), and by gallic acid representing hydroxybenzoic acids (C6 - C1 - structure). Further, the flavonoids, flavone, apigenin, kaempferol, quercetin and myricetin (C6 - C3 - C6 - structure) were also caused to react with soy proteins to estimate the influence of the number and the position of hydroxy substituents. The derivatization caused a reduction of lysine, cysteine and tryptophan residues in the soy proteins. The isoelectric points of the derivatives were shifted to lower pH values and formation of high molecular fractions was documented. The derivatives were characterized in terms of their solubility at different pH-values to document the influence on the functional properties. The structural changes induced were studied using circular dichroism (CD), differential scanning calorimetry (DSC) , intrinsic fluorescence, and binding of anilinonaphthalenesulfonic acid. The influence of derivatization on the in-vitro digestibility with trypsin, chymotrypsin, pepsin and pancreatin was also assessed. The effect on the trypsin inhibitor activity of all the resulting STI derivatives was studied, the latter being reduced. Y1 - 2002 ER - TY - JOUR A1 - Rawel, Harshadrai Manilal A1 - Rohn, Sascha A1 - Kruse, Hans-Peter A1 - Kroll, Jürgen T1 - Structural changes induced in bovine serum albumin by covalent attachment of chlorogenic acid N2 - Bovine serum albumin (BSA) was modifed by covalent attachment of chlorogenic acid using different concentrations at pH 9. The derivatization was accompanied by a reduction of lysine, cysteine and tryptophan residues. The isoelectric points were shifted to lower pH values and formation of high molecular weight fractions was noted. The structural changes were studied using circular dichroism, differential scanning calorimetry (DSC), intrinsic fluorescence, and binding of anilinonaphthalenesulfonic acid. The results showed that the content of alpha-helix decreased with a parallel increase in unordered structures with higher degrees of derivatization. DSC revealed a decrease in both denaturation temperature and enthalpy. Surface hydrophobicity declined, indicating that hydrophilic regions were exposed on the molecular surface. Proteolytic digestion showed that, at a lower degree of derivatization,the tryptic degradation was most adversely effected, whereas the peptic digestion declined with increasing modification. A trypsin inhibitory effect of the breakdown products released from derivatized BSA was also observed. Y1 - 2002 ER - TY - THES A1 - Rawel, Harshadrai Manilal T1 - Reactions of selected secondary plant metabolites (glucosinolates and phenols) with food proteins and enzymes- influence on physico-chemical protein properties, enzyme activity and proteolytic degradation Y1 - 2002 ER - TY - JOUR A1 - Rohn, Sascha A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen T1 - Inhibitory effects of plant phenols on the activity of selected enzymes N2 - Selected enzymes (alpha-amylase, trypsin, and lysozyme) were allowed to react with some simple phenolic and related compounds (caffeic acid, chlorogenic acid, ferulic acid, gallic acid, m-, o-, and p-dihydroxybenzenes, quinic acid, and p-benzoquinone). The derivatized enzymes obtained were characterized in terms of their activity. In vitro experiments showed that the enzymatic activity of the derivatives was adversely affected. This enzyme inhibition depended on the reactivity of the phenolic and related substances tested as well as on the kind of substrate applied. The decrease in the activity was accompanied by a reduction in the amount of free amino and thiol groups, as well as tryptophan residues, which resulted from the covalent attachment of the phenolic and related compounds to these reactive nucleophilic sites in the enzymes. The enzyme inhibition correlates well with the blocking of the mentioned amino acid side chains. Y1 - 2002 UR - http://pubs.acs.org/journals/jafcau/abstract.cgi/jafcau/2002/50/i12/abs/jf011714b.html ER - TY - JOUR A1 - Rohn, Sascha A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen T1 - Influence of plant phenols on selected enzymes N2 - Secondary plant metabolites are important native food components, which are becoming more and more interesting due to their physiological effects on humans. Some representatives of these compounds are very reactive and can interact with other main food components like proteins resp. enzymes. This work deals with the reactions of selected enzymes (trypsin, alpha-chymotrypsin and alpha-amylase) with simple phenolic and related substances (caffeic acid, chlorogenic acid, ferulic acid, gallic acid, meta-, ortho- and para-dihydroxybenzene, 1,4-benzoquinone, quinic acid). The derivatives formed were characterized in terms of their activity and selected physicochemical properties. In vitro experiments showed that the proteolytic digestion of food proteins with trypsin and alpha-chymotrypsin derivatives was adversely affected. This decrease depends on the reactivity of the phenolic and related substances tested as well as on the kind of substrate applied. Reactions of phenolic compounds with other enzymes (alpha-amylase and lysozyme) showed similar results with regard to physicochemical properties and their activities. Y1 - 2002 ER - TY - JOUR A1 - Kroll, Jürgen A1 - Rawel, Harshadrai Manilal A1 - Czajka, Dörte T1 - Changes induced in properties of food proteins by apigenin and quercetin N2 - Selected food proteins (myoglobin and soy glycinin) were caused to react with flavonoids (apigenin and quercetin) to estimate the influence of the number and the position of hydroxy substituents. The protein derivatives formed have been charcterized in terms of their properties where they showed changes in the content of free amino groups, tryptophan, and thiol groups. The myoglobin derivatives have also been characterized in terms of their solubility at different pH-values to document the influence on the functional properties. The influence of myoglobin derivatives on the in vitro digestibility with trypsin was also demonstrated, with the digestion of the derivatized myoglobin being favored. Y1 - 2002 ER - TY - JOUR A1 - Kroll, Jürgen A1 - Rawel, Harshadrai Manilal A1 - Rohn, Sascha T1 - Reactions of plant phenolics with food proteins and enzymes under special consideration of covalent bonds : a Review Y1 - 2003 ER -