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

Abstract

Hydrogen sulfide (H 2 S) 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 H 2 S transfer toward these metaquo-hemeproteins. In this sol-gel environment, metHbI binds and releases H 2 S with rate constants of 0.0597 M -1 · s -1 and 6.67 × 10 -5 s -1 , respectively. The process generates an H 2 S affinity constant (k on /k off ) of 8.9 × 10 2 M -1 , which is 10 7 lowers than the analogous constant in solution (6.3 × 10 9 M -1 ). Although the H 2 S k off for the rHbI-H 2 S complex is almost similar with both sol-gel and solution. To further understand how the H 2 S k off from rHbI-H 2 S 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 H 2 S transfer from a solution of the rHbI-H 2 S complex to encapsulated hemeprotein resulted in k off values of 1.90 × 10 -4 s -1 , and 2.09 × 10 -4 s -1 leading to the formation of rHbI-H 2 S and Mb-H 2 S species, respectively. The results suggest that the: 1) extreme ionic TMOS construct limits the H 2 S pathways to reach the hemeprotein active center, 2) possible interaction with metHbI hydrophilic forces increases the hydrogen bonding networking and decreases the H 2 S 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-H 2 S 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 H 2 S from solution or gas media.