Figure 6. Effects of disulfide bonding on HGDC conformation induced by UV-C irradiation. A: Reducing (with β-mercaptoethanol) SDS-PAGE analysis of irradiated HGDC samples (1 mg/ml; M: protein marker, Lane 1: 0 min, Lane 2: 10 min, Lane 3: 20 min, Lane 4: 30 min, Lane 5: 40 min, Lane 6: 50 min, Lane 7: 60 min). B: Effects of L-cysteine on the turbidity of UV-C irradiated HGDC. The concentrations of L-cysteine and HGDC were 2 mM and 1 mg/ml. Inset: photograph of UV-C irradiated HGDC samples with and without L-cysteine (1): 2 mM L-cysteine without UV-C irradiation, (2): 1 mg/ml HGDC without UV-C irradiation, (3): mixture of 1 mg/ml HGDC and 2 mM L-cysteine without UV-C irradiation, (4): 2 mM L-cysteine with 60 min-UV-C irradiation, (5): 1 mg/ml HGDC with 60 min-UV-C irradiation, (6): mixture of 1 mg/ml HGDC and 2 mM L-cysteine with 60 min-UV-C irradiation). C: Non-reducing (without β-mercaptoethanol) SDS–PAGE analysis of 2 mM L-cysteine-HGDC mixture upon UV-C irradiation (M: protein marker, Lane 1: initial HGDC, Lane 2: UV-C irradiated HGDC (30 min-exposure), Lane 3: UV-C irradiated HGDC (60 min-exposure), Lane 4: initial 2 mM L-cysteine-HGDC mixture, Lane 5: UV-C irradiated 2 mM-L-cysteine-HGDC mixture (30 min-exposure), Lane 6: UV-C irradiated 2 mM-L-cysteine-HGDC mixture (60 min-exposure), Lane 7: L-cysteine-treated HGDC sample, Lane 8: 30 min UV-C exposed L-cysteine-treated HGDC sample, Lane 9: 60 min UV-C exposed L-cysteine-treated HGDC sample. L-cysteine-treated HGDC samples for Lanes 7–9 were obtained according to the following procedure: HGDC was first incubated with 2 mM L-cysteine for 12 h. The resultant L-cysteine-HGDC mixtures were then transferred to a Vivaspin 6 centrifugal concentrator filter unit with nominal molecular weight limit (NMWL) of 5 kDa (Sartorius, Gottingen, Germany). Followed by spinning at 4,307 rpm for 30 min, L-cysteine was removed from HGDC samples.