Consequential secondary structure alterations and aggregation during prolonged casein glycation

Abstract

Non-enzymatic glycosylation (glycation) of casein is a process used not just to ameliorate the quality of dairy products but also to increase the shelf life of canned foods, including baby milk supplements. Incubation of κ-casein with reducing sugars for 15 days at physiological temperature showed the formation of a molten globule state at day 9 and 12 during fructation and glucation respectively. This state exhibits substantial secondary structure and maximum ANS binding. Later on, glycation resulted in the formation of aggregates at day 12 in presence of fructose and day 15 in presence of glucose. Aggregates possess extensive β-sheet structure as revealed by far-UV CD and FTIR. These aggregates showed altered tryptophan environment, decrease ANS binding relative to molten globule state and increase in Thioflavin T fluorescence. Aggregates were also accompanied by the accumulation of AGEs, indicative of structural damage to the protein and formation of potentially harmful species at the physiological level. Fructose was more reactive than glucose and thus caused early and significant changes in the protein. From our studies, we conclude that controlling the extent of the Maillard reaction in the food industry is essential to counter its negative effects and expand its safety spectrum.

Thermal Fourier Transform Infrared Technique Quickly Detects an Early Onset of Glycation-Induced Conformational Changes of Human Serum Albumin

“…The ribosylation is responsible for the conformational changes, leading to an increase in total β-conformation, particularly the excess increases in the formation of intermolecular beta-sheet structures. This was consistent with the results of glycated albumin due to the conformational change from its native α-helical to β-sheeted structures [64][65], resulting in the formation of protein aggregation and fibrillation [65][66][67][68].…”

Design of bio-based supramolecular structures through self-assembly of α-lactalbumin and lysozyme

“…6 it is possible to conclude that a-LaeLys supramolecular structures prepared at both pH values (i.e. pH 3 and 11), when treated at 25 C for 15 and 35 min, maintained the overall characteristics expected for an a-helix-rich protein structure (Greenfield, 1999;Jindal & Naeem, 2013) e Fig. 6a and b.…”

“…The native spectrum of a-La and Lys exhibited a negative peak at 208 nm (more prominent) and a large band with negative ellipticity intensity at ca. 222 nm indicating that the secondary structures of those proteins are rich in a-helices (Greenfield, 1999;Jindal & Naeem, 2013); however native a-La displayed a peak with higher negative signal intensity than Lys. A similar behavior was found by He et al (2013) for native a-La and Lys prepared at 1.5 mg mL À1 , by Diniz et al (2014) for native a-La, prepared at 1.5 mg mL À1 and by Bob aly et al (2014) for native Lys prepared at 2.3 mg mL À1 ; these authors observed negative peaks at approximately 208 and 222 nm, which are typical of well-defined a-helix-rich proteins.…”

Production, characterization and foamability of α-lactalbumin/glycomacropeptide supramolecular structures

“…In addition, an increase in peak emission intensity was observed. These findings indicate that the surrounding chemical environment of the chromophores became more apolar (Jindal & Naeem, 2013;Taheri-Kafrani, Asgari-Mobarakeh, Bordba, & Haertlé, 2010;Taheri-Kafrani, Bordbar, Mousavi, & Haertlé, 2008;Zhang, Qi, Zheng, Li, & Liu, 2009), suggesting that during the interaction between α-la and GMP molecules, the chromophores remain buried deeper in the core structures composed of these molecules ( Fig. 4a and b).…”