Using DSC, the thermal unfolding of RNase A, RNase B, and two partly deglycosylated RNase B forms was studied. The oligosaccharide side chain leads to slight protein stabilization. The conformational stability at pH 4.0 amounts to DeltaG(25degreesC) = 34.5, 34.6, 33.7, and 32.8 kJ mol(-1) for RNase B, Man(1)-RNase, GlnNAc(1)-RNase, and RNase A, respectively. The heat capacity remains the same for glycosylated and deglycosylated protein. These results are consistent with a proposed hydrogen bond of Lys37 with GlnNAc-1.