Transfer and Reactivity of Hydrogen Sulfide with Immobilized Hemeproteins in Polymeric Matrix

Hydrogen sulfide (H2S) has been related to be toxic and to have a role in human physiological functions. Therefore, there is a necessity to comprehend ways to scavenger hydrogen sulfide from different media. Here, we used recombinant metaquo-Hemoglobin I (metHbI) from Lucina pectinata and metaquo-myoglobin (metMb) encapsulated in the tetramethyl orthosilicate gel (TMOS), to facilitate the understanding of H2S transfer toward these metaquo-hemeproteins. In this sol-gel environment, metHbI binds and releases H2S with rate constants of 0.0597 M-1·s-1 and 6.67 × 10-5 s-1, respectively. The process generates an H2S affinity constant (kon/koff) of 8.9 × 102 M-1, which is 107 lowers than the analogous constant in solution (6.3 × 109 M-1). Although the H2S koff for the rHbI-H2S complex is almost similar with both sol-gel and solution. To further understand how the H2S koff from rHbI-H2S in solution (5 μM) is influenced by the protein concentration gradient, metHbI and metMb (25 μM) encapsulated in TMOS sol-gel. Under these circumstances, the H2S transfer from a solution of the rHbI-H2S complex to encapsulated hemeprotein resulted in koff values of 1.90 × 10-4 s-1, and 2.09 × 10-4 s-1 leading to the formation of rHbI-H2S and Mb-H2S species, respectively. The results suggest that the: 1) extreme ionic TMOS construct limits the H2S pathways to reach the hemeprotein active center, 2) possible interaction with metHbI hydrophilic forces increases the hydrogen bonding networking and decreases the H2S association constant, 3) hemeproteins concentration gradients between solution and sol-gels also influence its hydrogen sulfide transfer. In the presence of oxygen or hydrogen peroxide metMb generated a mixture of Mb-H2S and sulfmyoglobin derivative, while encapsulated metHbI reaction did not produce the sulfheme species. Consequently, the results show that metHbI encapsulated in TMOS is an excellent trap for H2S from solution or gas media.