Mono- and bis-phosphine-ligated H93G myoglobin: spectral models for ferrous-phosphine and ferrous-CO cytochrome P450

Effect of Cross-Linkers on Mussel- and Elastin-Inspired Adhesives on Physiological Substrates

Surgical adhesives can be useful in wound closure because they reduce the risk of infection and pain associated with sutures and staples. However, there are no commercially available surgical adhesives for soft tissue wound closure. To be effective, soft tissue adhesives must be soft and flexible, strongly cohesive and adhesive, biocompatible, and effective in a moist environment. To address these criteria, we draw inspiration from the elasticity and resilience of elastin proteins and the adhesive of marine mussels. We used an elastin-like polypeptide (ELP) for the backbone of our adhesive material due to its elasticity and biocompatibility. A mussel-inspired adhesive molecule, l-3,4-dihydroxyphenylalanine (DOPA), was incorporated into the adhesive to confer wet-setting adhesion. In this study, an ELP named YKV was designed to include tyrosine residues and lysine residues, which contain amine groups. A modified version of YKV, named mYKV, was created through enzymatic conversion of tyrosine residues into DOPA. The ELPs were combined with iron(III) nitrate, sodium periodate, and/or tris(hydroxymethyl)phosphine (THP) cross-linkers to investigate the effect of DOPA- and amine-based cross-linking on adhesion strength and cure time on porcine skin in a warm, humid environment. Incorporation of DOPA into the ELP increased adhesive strength by 2.5 times and reduced failure rates. Iron cross-linkers improved adhesion in the presence of DOPA. THP increased adhesion for all proteins tested even in the absence of DOPA. Using multiple cross-linkers in a single formulation did not significantly improve adhesion. The adhesives with the highest performance (iron nitrate mixed with mYKV and THP mixed with YKV or mYKV) on porcine skin had 10-18 times higher adhesion than a commercial sealant and reached appreciable adhesive strength within 10 min.

Redox Regulation of Heme Oxygenase-2 and the Transcription Factor, Rev-Erb, Through Heme Regulatory Motifs

SIGNIFICANCE

Heme binds to and serves as a cofactor for a myriad of proteins that are involved in diverse biological processes. Hemoproteins also exhibit varying modes of heme binding, suggesting that the protein environment contributes to the functional versatility of this prosthetic group. The subject of this review is a subset of hemoproteins that contain at least one heme regulatory motif (HRM), which is a short sequence containing a Cys-Pro core that, in many cases, binds heme with the Cys acting as an axial ligand. Recent Advances: As more details about HRM-containing proteins are uncovered, some underlying commonalities are emerging, including a role in regulating protein stability. Further, the cysteines of some HRMs have been shown to form disulfide bonds. Because the cysteines must be in the reduced, dithiol form to act as a heme axial ligand, heme binds at these sites in a redox-regulated manner, as demonstrated for heme oxygenase-2 (HO2) and Rev-erbβ.

CRITICAL ISSUES

HRM-containing proteins have wide variations in heme affinity, utilize different axial ligand schemes, and exhibit differences in the ability to act as a redox sensor-all while having a wide variety of biological functions. Here, we highlight HO2 and Rev-erbβ to illustrate the similarities and differences between two hemoproteins that contain HRMs acting as redox sensors.

FUTURE DIRECTIONS

HRMs acting as redox sensors may be applicable to other HRM-containing proteins as many contain multiple HRMs and/or other cysteine residues, which may become more evident as the functional significance of HRMs is probed in additional proteins.

Six-Coordinate Ferrous Nitrosyl Complex FeII(TTP)(PMe3)(NO) (TTP = meso-Tetra-p-tolylporphyrinato Dianion)

Low-temperature in situ Fourier transform infrared and UV-vis measurements show that trimethylphosphine (PMe₃) reacts with microporous layers of Fe^II(TTP)(NO) (TTP = meso-tetra-p-tolylporphyrinato dianion; NO = nitric oxide) to form the previously unknown six-coordinate complex Fe^II(TTP)(PMe₃)(NO). Upon warming this compound to room temperature in the presence of excess phosphine, the NO ligand is completely replaced by phosphine, resulting in formation of the bis(trimethylphosphine) complex Fe^II(TTP)(PMe₃)₂. Simultaneously, the NO released oxidizes free PMe₃ to the corresponding phosphine oxide (OPMe₃) with concomitant formation of nitrous oxide (N₂O).