Supramolecular Regulation of Polydopamine Formation by Amyloid Fibers

Polydopamine (PD) and melanin species are chemically complex systems, the formation and properties of which are incompletely understood. Inspired by the role of functional amyloids in melanin biosynthesis, this paper examines the influences of the supramolecular structure of amyloids on oxidative polymerization of dopamine. Kinetic analyses on the formation of PD species in the presence of hen egg white lysozyme (HEWL) fibers or soluble HEWL revealed that both forms gave rise to the total quantity of PD species, but the rate of their formation could be accelerated only by the amyloid form. PD species formed with HEWL fibers showed a morphology of bundled fibers, whereas those with soluble HEWL had a mesh-like structure. Amyloid fibers of recombinant Pmel17 had properties similar to those of HEWL fibers in modulating PD formation. The results presented here suggest how nature designs functionality with an amyloid structure and can help understand and engineer chemistries of other functional amyloids.     

Interprotein Electron Transfer between FeS-Protein Nanowires and Oxygen-Tolerant NiFe Hydrogenase

Self-assembled redox protein nanowires have been exploited as efficient electron shuttles for an oxygen-tolerant hydrogenase. An intra/inter-protein electron transfer chain has been achieved between the iron-sulfur centers of rubredoxin and the FeS cluster of [NiFe] hydrogenases. [NiFe] Hydrogenases entrapped in the intricated matrix of metalloprotein nanowires achieve a stable, mediated bioelectrocatalytic oxidation of H₂ at low-overpotential.     

Computer-aided molecular modeling of polymers. III. enthalpy of polymerization as a measure of stability

A formalism of computational chemistry methods is presented to estimate the stability of vinyl polymers. This approach takes into account changes in electronic energy upon polymerization using quantum mechanical methods and contributions of the conformational energetics of the polymerized state using a molecular mechanics force field. A work term, ΔV, based upon the molecular volume difference between the monomer and the reactant, is shown to be negligible. For 10 structurally diverse vinyl polymers, the sum of the electronic and conformational energy differences between reactant and monomer states, AEp, has a high linear correlation with corresponding measured enthalpies of polymerization, ΔHp. The linear regression least square fit is ΔHp = 0.89 AEp-13.39. Errors due to possible contributions to AHp not included in the formalism reported here are probably small and/or relatively constant over the set of polymers studied. If this were not the case, a linear correlation between AHp and AEp, with a slope near 1, would not be observed. Most likely the intercept of-13.39 kcal/mol is due to the choice of the quantum mechanical method used, MNDO. Overall, the formalism presented here seems a reliable means of predicting relative polymerization stability, in advance of synthesis, for a structurally congeneric set of polymers.     

Amyloid-like fibril-forming supramolecular β-sheets from a β-turn forming tripeptide containing non-coded amino acids: the crystallographic signature

The crystal structure of a terminally protected tripeptide Boc-Leu-Aib-β-Ala-OMe 1 containing non-coded amino acids reveals that it adopts a β-turn structure, which self-assembles to form a supramolecular β-sheet via non-covalent interactions. The SEM image of peptide 1 exhibits amyloid-like fibrillar morphology in the solid state.