Understanding Proton Transfer in Non-aqueous Biopolymers based on Helical Peptides: A Quantum Mechanical Study

Histidine (an imidazole-based amino acid) is a promising building block for short aromatic peptides containing a proton donor/acceptor moiety. Previous studies have shown that polyalanine helical peptides substituted at regular intervals with histidine residues exhibit both structural stability as well as high proton affinity and high conductivity. Here, we present first-principle calculations of non-aqueous histidine-containing 310-,  and -helices and show that they are able to form hydrogen-bonded networks mimicking proton wires that have the ability to shuttle protons via the Grotthuss shuttling mechanism. The formation of these wires enhances the stability of the helices, and our structural characterizations confirm that the secondary structures are conserved despite distortions of the backbones. In all cases, the helices exhibit high proton affinity and proton transfer barriers on the order of 1~4 kcal/mol. Zero-point energy calculations suggest that for these systems, ground state vibrational energy can provide enough energy to cross the proton transport energy barrier. Additionally, ab initio molecular dynamics results suggests that the protons are transported unidirectionally through the wire at a rate of approximately 2 Å every 20 fs. These results demonstrate that efficient deprotonation-controlled proton wires can be formed using non-aqueous histidine-containing helical peptides.

Comprehensive Analysis and Biological Characterization of Venom Components from Solitary Scoliid Wasp Campsomeriella annulata annulata

Venoms of solitary wasps are utilized for prey capture (insects and spiders), paralyzing them with a stinger injection to be offered as food for their larvae. Thus, the identification and characterization of the components of solitary wasp venoms can have biotechnological application. In the present study, the venom components profile of a solitary scoliid wasp, Campsomeriella annulata annulata, was investigated through a comprehensive analysis using LC-MS and -MS/MS. Online mass fingerprinting revealed that the venom extract contains 138 components, and MS/MS analysis identified 44 complete sequences of the peptide components. The peptides are broadly divided into two classes: bradykinin-related peptides, and linear α-helical peptides. Among the components of the first class, the two main peptides, α-campsomerin (PRLRRLTGLSPLR) and β-campsomerin (PRLRRLTGLSPLRAP), had their biological activities evaluated. Both peptides had no effects on metallopeptidases [human neprilysin (NEP) and angiotensin-converting enzyme (ACE)] and acetylcholinesterase (AChE), and had no cytotoxic effects. Studies with PC12 neuronal cells showed that only α-campsomerin was able to enhance cell viability, while β-campsomerin had no effect. It is noteworthy that the only difference between the primary structures from these peptides is the presence of the AP extension at the C-terminus of β-campsomerin, compared to α-campsomerin. Among the linear α-helical peptides, annulatin (ISEALKSIIVG-NH2) was evaluated for its biological activities. Annulatin showed histamine releasing activity from mast cells and low hemolytic activity, but no antimicrobial activities against all microbes tested were observed. Thus, in addition to providing unprecedented information on the whole components, the three peptides selected for the study suggest that molecules present in solitary scoliid wasp venoms may have interesting biological activities.

Implicit solvent models fail to reproduce secondary structures of de novo designed peptides

We test a range of standard implicit solvent models and protein forcefields for a set of 5 experimentally characterized, designed α-helical peptides. 65 combinations of forcefield and implicit solvent models are evaluated in >800 µs of molecular dynamics simulations. The data show that implicit solvent models generally fail to reproduce the experimentally observed secondary structure content, and none performs well for all 5 peptides. The results show that these models are not usefully predictive.

Bioactive properties of insect products for monogastric animals – a review

Insects or products derived from insects are considered as a valuable feed ingredient for aquaculture, poultry, and pigs but also exert possible secondary effects of health stimulators in livestock as reported in literature. Health benefits attributed to insects can create additional value in the insect chain. Three categories of bioactive compounds in insects are reported in this desk study: antimicrobial peptides (such as α-helical peptides, cysteine-rich peptides, proline-rich peptides, glycine-rich peptides), fatty acids (especially lauric acid), and polysaccharides (especially chitin and chitosan). The review summarises the recent literature on these three categories. Antimicrobial properties or immuno-modulating effects may contribute to reduce the use of antibiotics and to avoid antibiotic resistance in livestock when these insect products are included in animal diets. Furthermore, antioxidant capacity of insect-proteins might reduce collateral tissue damage. Health stimulating effects of insect products may result in additional applications of insect products in animal feed for livestock.