Theoretical investigation on the reaction of adhesion unit dopa in mussel with electrolyzing seawater.

Adhesive proteins secreted by the marine mussel could bind strongly to all kinds of surfaces, for instance, ship hulls and petroleum pipelines. Studies indicated that there was an unusual amino acid 3,4-dihydroxy-l-phenylanine (dopa), which was the crucial super adhesive unit in the proteins. The technology of electrolyzing seawater was employed to generate HOCl solution to hinder the adhesion. However, the detailed anti-fouling mechanism of HOCl solution remained unknown to be fully explained. Herein, we theoretically reported a study of single molecular (dopa) reaction under the HOCl solution environment, which would be helpful to reveal the anti-fouling mechanism through electrolyzing seawater. By using the density functional theory (DFT) quantum mechanics procedure, we theoretically studied the reaction mechanism of the adhesive unit dopa in mussel with electrolyzing seawater. Two possible pathways (1 and 2) were obtained (Fig. 6). The transition state for each pathway was determined, the intrinsic reaction coordinate (IRC) was analyzed and the mechanism had been confirmed. The calculations indicated dopa tended to have electrophonic attacking substitution reaction to generate 3-chlorine-4,5-dihydroxyphenylalanine (dopa-Cl) with different pathways, which hindered the formulation of conjuncted dopa-dopa and thus the stickiness among mussel adhesive proteins reduced. The transition states computation showed that pathway (1) had one transition state (TS1-1) with an activation energy of 102.22 kJ mol(-1), while pathway (2) had two transition states (TS2-1, TS2-2) with activation energies of 191.98 kJ mol(-1) and 42.00 kJ mol(-1) respectively and one intermediate (IM2-1). Rate constant value of pathway (1) was much bigger than that of pathway (2) regardless of high or low temperature, which meant that in the reaction process, pathway (1) was the favorable reaction step; but as the temperature rose, the competitiveness of pathway (2) gradually increased. After the theoretical calculation, we found that it was Cl(+) played an important and direct role in the dopa's modification.

Characteristics of virulence gene in Vibrio parahaemolyticus strains isolated from clinical patients and environment in Hangzhou, China / 中华预防医学杂志

<p><b>OBJECTIVES</b>To investigate the characteristics of virulence gene in Vibrio parahaemolyticus strains isolated from clinical patients and environment in Hangzhou, China.</p><p><b>METHODS</b>Thermostable direct hemolysin gene (tdh) and thermostable direct hemolysin-related hemolysin gene (trh) were determined in a total of 174 strains of V. parahaemolyticus isolated from patients and environment (seafood) in Hangzhou area by PCR.</p><p><b>RESULTS</b>The tdh was found in 92 out of 94 V. parahaemolyticus strains from food poisoning patients and in 33 out of 34 strains from sporadic diarrhea patients, and trh was not detected in all above clinical strains. Meanwhile the tdh was negative in all V. parahaemolyticus strains from environment, and the trh was also negative except one strain with urease activity. All strains with trh negative had no the activity of urease.</p><p><b>CONCLUSIONS</b>The V. parahaemolyticus strains from food poisoning patients and sporadic diarrhea patients are tdh positive and trh negative. The V. parahaemolyticus strains with tdh negative and almost trh positive in environment might be a potential pathogen in Hangzhou.</p>