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Structural features of bovine caseinomacropeptide A and B by 1H nuclear magnetic resonance spectroscopy

Published online by Cambridge University Press:  17 June 2002

MARK H. SMITH
Affiliation:
Food Science Section, New Zealand Dairy Research Institute, Palmerston North, New Zealand Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
PATRICK J. B. EDWARDS
Affiliation:
Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
KATE P. PALMANO
Affiliation:
Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
LAWRENCE K. CREAMER
Affiliation:
Food Science Section, New Zealand Dairy Research Institute, Palmerston North, New Zealand

Abstract

Samples of bovine caseinomacropeptide (CMP) were isolated from κ-casein A and κ-casein B and fractionated to give aglycosylated CMP A and CMP B and monoglycosylated CMP A. The secondary structures of these three peptides were compared under neutral and acidic (pH 4·2) conditions, using two-dimensional (2D) 1H nuclear magnetic resonance (NMR) spectroscopy. The differences between the spectra at pH 4·2 and 7·0 and the spectra of the aglycosylated and glycosylated CMP A were subtle, indicating little change in backbone conformation with these changes. These results suggest that differences in the coagulation properties of milks containing either κ-casein A or κ-casein B are more likely to be related to factors, such as micelle size or charge, than to structural differences arising from altered backbone conformation of the macropeptide segments of the κ-caseins.

Type
Research Article
Copyright
Proprietors of Journal of Dairy Research 2002

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