The Role of Salt Bridge Formation in Glucagon: An Experimental and Theoretical Study of Glucagon Analogs and Peptide Fragments of Glucagon

Understanding the Role of Intramolecular Ion-Pair Interactions in Conformational Stability Using an Ab Initio Thermodynamic Cycle

Intramolecular ion-pair interactions yield shape and functionality to many molecules. With proper orientation, these interactions overcome steric factors and are responsible for the compact structures of several peptides. In this study, we present a thermodynamic cycle based on isoelectronic and alchemical mutation to estimate the intramolecular ion-pair interaction energy. We determine these energies for 26 benchmark molecules with common ion-pair combinations and compare them with results obtained using intramolecular symmetry-adapted perturbation theory. For systems with long linkers, the ion-pair energies evaluated using both approaches deviate by less than 2.5% in the vacuum phase. The thermodynamic cycle based on density functional theory facilitates calculations of salt-bridge interactions in model tripeptides with continuum/microsolvation modeling and four large peptides: 1EJG (crambin), 1BDK (bradykinin), 1L2Y (a mini-protein with a tryptophan cage), and 1SCO (a toxin from the scorpion venom).

Effects of octacosanol extracted from rice bran on blood hormone levels and gene expressions of glucose transporter protein-4 and adenosine monophosphate protein kinase in weaning piglets

The object of this study was to explore the regulatory mechanism of octacosanol to the body of animals and the effects of octacosanol on blood hormone levels and gene expressions of glucose transporter protein (GLUT-4) and adenosine monophosphate protein kinase (AMPK) in liver and muscle tissue of weaning piglets. A total of 105 crossbred piglets ([Yorkshire × Landrace] × Duroc) with an initial BW of 5.70 ± 1.41 kg (21 d of age) were used in a 6-wk trial to evaluate the effects of octacosanol and tiamulin supplementation on contents of triiodothyronine (T₃), thyroxine (T₄), growth hormone (GH), glucagon (GU) and adrenaline (AD) in blood and gene expressions of GLUT-4 and AMPK in liver and muscle. Piglets were randomly distributed into 3 dietary treatments on the basis of BW and sex. Each treatment had 7 replicate pens with 5 piglets per pen. Treatments were as followed: control group, tiamulin group and octacosanol group. The results showed that compared with control group and tiamulin group, octacosanol greatly promoted the secretion of T₃, GH, GU and AD (P < 0.01) and significantly up-regulated the gene expressions of GLUT-4 and AMPK in muscle and liver tissues (P < 0.05). There was no significant difference between the control group and tiamulin group in T₃, T₄, GH, GU or AD (P > 0.05). Results of the present study has confirmed that octacosanol affects energy metabolism of body by regulating secretion of blood hormones and related gene expression in tissue of weaning piglets, which can reduce stress response and has an impact on performance.

Chemically surface modified gel (CSMG): An excellent enzyme-immobilization matrix for industrial processes

Invertase from S. cerevisiae has been immobilized on porous silica matrix, formed using sol-gel chemistry, with surface area of approximately 650 m(2)/g. The co-condensation of silica sol with 3-aminopropyl(triethoxy)silane produced an amino-chemically surface modified silica gel (N-CSMG) with a very high ligand loading of 3.6 mmol/g SiO(2); significantly higher than commercially available matrices. Surface amine groups were activated with glutaraldehyde to produce GA-N-CSMG, and invertase covalently attached by the aldehyde. Invertase was used as a model enzyme to measure the immobilizing character of the GA-N-CSMG material. Using an optimized immobilization protocol, a very high loading of 723 mg invertase per gram GA-N-CSMG is obtained; 3-200-fold higher than values published in literature. The reproducible, immobilized activity of 246,000 U/g GA-N-CSMG is also greater than any other in literature. Immobilized invertase showed almost 99% retention of free enzyme activity and no loss in catalytic efficiency. The apparent kinetic parameters K(M) and V(M) were determined using the Michealis-Menten kinetic model. K(M) of the free invertase was 1.5 times greater than that of the immobilized invertase--indicating a higher substrate affinity of the immobilized invertase. These findings show considerable promise for this material as an immobilization matrix in industrial processes.