Understanding the Interaction Mechanism between the Epinephrine Neurotransmitter and Small Gold Nanoclusters (Aun; n = 6, 8, and 10): A Computational Insight.

In this study, the interaction between the neurotransmitter epinephrine and small gold nanoclusters (AunNCs) with n = 6, 8, and 10 is described by density functional theory calculations. The interaction of Au6, Au8, and Au10 nanoclusters with epinephrine is governed by Au-X (X = N and O) anchoring bonding and Au···H-X conventional hydrogen bonding. The interaction mechanism of epinephrine with gold nanoclusters is investigated in terms of electronic energy and geometrical properties. The adsorption energy values for the most favorable configurations of Au6NC@epinephrine, Au8NC@epinephrine, and Au10NC@epinephrine were calculated to be -17.45, -17.86, and -16.07 kcal/mol, respectively, in the gas phase. The results indicate a significant interaction of epinephrine with AunNCs and point to the application of the biomolecular complex AunNC@epinephrine in the fields of biosensing, drug delivery, bioimaging, and other applications. In addition, some important electronic properties, namely, the energy gap between HOMO and LUMO, the Fermi level, and the work function, were computed. The effect of aqueous media on adsorption energy and electronic parameters for the most favorable configurations was also studied to explore the influence of physical biological conditions.

Practical procedures for genetic manipulation systems for medermycin-producing Streptomyces sp. AM-7161.

Streptomyces sp. AM-7161 is a producer of an aromatic polyketide medermycin with strong antibacterial and antitumor activity. It has been inefficient to perform genetic manipulations in this strain, which heavily hinders the genetic analysis of some interesting problems concerning tailoring modifications in medermycin biosynthesis. Here, condition optimizations of sporulation and mycelium growth of this strain as well as protoplast preparation and regeneration were conducted systematically. Based on these results, protoplast transformation system was established, and two types of foreign plasmids (integrative and auto-replicating) were efficiently introduced into this strain. Additionally, a conjugation system to mediate plasmid transfer between Escherichia coli and Streptomyces sp. AM-7161 was also optimized and established. These results provide the practical procedures to perform more convenient genetic analysis of medermycin biosynthesis in this strain.