Interpersonal relationships and suicidal ideation among Chinese youths: A network analysis.

BACKGROUND: Suicidal ideation is a noteworthy health problem that requires further study in the field of interpersonal relationships. The main scope of relationships include family, teachers, peers, and the Internet. However, few studies have considered the effects of interpersonal interactions. Based on the Interpersonal Theory of Suicide, this study explores the relation between different interpersonal relationships and suicidal ideation. METHODS: A network analysis approach was used to test the relationships. Cross-sectional data (N = 1694; 52.1 % boys; Mage = 11.86 years, SD = 1.59) were collected from primary and secondary students in October-November 2022. Participants completed a survey including demographic part and questionnaires: Positive and Negative Suicide Ideation Inventory (PANSI), Interpersonal Needs Questionnaire (INQ), Family Adaptability and Cohesion Evaluation Scale (FACES II), Inventory of Parent and Peer Attachment (IPPA), Student-Teacher Relationship Scale (STRS) and Facebook Intensity Scale (FIS). RESULTS: All variables showed a significant correlation in this inferred network. Family, teacher-student, and peer relationships are protective against suicidal ideation. The closeness of the teacher-student relationship showed the highest strength centrality. However, online interpersonal relationship is a risk factor for suicide. Thwarted belongingness and perceived burdensomeness are proximal factors of suicidal ideation that influenced all interpersonal relationships. LIMITATIONS: The network analysis as a data-driven and exploratory method may be limited to provide exact cause and effect relationship. CONCLUSIONS: This study shows that teacher-student connections may be more important than other relationships of young people. Improper peer and online interpersonal relationship could be risky for suicide. Further studies are needed to examine the role of these relationships elaborately.

Rational generation of lasso peptides based on biosynthetic gene mutations and site-selective chemical modifications.

Lasso peptides are a unique family of natural products whose structures feature a specific threaded fold, which confers these peptides the resistance to thermal and proteolytic degradation. This stability gives lasso peptides excellent pharmacokinetic properties, which together with their diverse reported bioactivities have garnered extensive attention because of their drug development potential. Notably, the threaded fold has proven quite inaccessible by chemical synthesis, which has hindered efficient generation of structurally diverse lasso peptides. We herein report the discovery of a new lasso peptide stlassin (1) by gene activation based on a Streptomyces heterologous expression system. Site-directed mutagenesis on the precursor peptide-encoding gene is carried out systematically, generating 17 stlassin derivatives (2-17 and 21) with residue-replacements at specific positions of 1. The solution NMR structures of 1, 3, 4, 14 and 16 are determined, supporting structural comparisons that ultimately enabled the rational production of disulfide bond-containing derivatives 18 and 19, whose structures do not belong to any of the four classes currently used to classify lasso peptides. Several site-selective chemical modifications are first applied on 16 and 21, efficiently generating new derivatives (20, 22-27) whose structures bear various decorations beyond the peptidyl monotonicity. The high production yields of these stlassin derivatives facilitate biological assays, which show that 1, 4, 16, 20, 21 and 24 possess antagonistic activities against the binding of lipopolysaccharides to toll-like receptor 4 (TLR4). These results demonstrate proof-of-concept for the combined mutational/chemical generation of lasso peptide libraries to support drug lead development.

Functional characterization and structural bases of two class I diterpene synthases in pimarane-type diterpene biosynthesis.

Pimarane-type diterpenoids are widely distributed in all domains of life, but no structures or catalytic mechanisms of pimarane-type diterpene synthases (DTSs) have been characterized. Here, we report that two class I DTSs, Sat1646 and Stt4548, each accept copalyl diphosphate (CPP) as the substrate to produce isopimara-8,15-diene (1). Sat1646 can also accept syn-CPP and produce syn-isopimaradiene/pimaradiene analogues (2-7), among which 2 possesses a previously unreported "6/6/7" ring skeleton. We solve the crystal structures of Sat1646, Sat1646 complexed with magnesium ions, and Stt4548, thereby revealing the active sites of these pimarane-type DTSs. Substrate modeling and subsequent site-directed mutagenesis experiments demonstrate different structural bases of Sat1646 and Stt4548 for 1 production. Comparisons with previously reported DTSs reveal their distinct carbocation intermediate stabilization mechanisms, which control the conversion of a single substrate CPP into structurally diverse diterpene products. These results illustrate the structural bases for enzymatic catalyses of pimarane-type DTSs, potentially facilitating future DTS engineering and combinatorial biosynthesis.

Discovery and Biosynthesis of Pepticinnamins G-M Featuring Three Enzymes-Catalyzed Nonproteinogenic Amino Acid Formation.

Since pepticinnamin E was discovered almost 30 years ago, no other pepticinnamin family of natural products has been reported to date. Here, we report the discovery of pepticinnamins G-I (1-3) from a marine Streptomyces sp. PKU-MA01144 and pepticinnamins J-M (4-7) from several mutants, and these new compounds contain different N-methyl-l-alanine and l-tyrosine residues compared to pepticinnamin E. Genome sequencing, heterologous expression, gene deletion, and reconstitution of enzymatic reaction in vitro identified the biosynthetic gene cluster of 1-7 and first experimentally established the biosynthesis of the nonproteinogenic 2-chloro-3-hydroxy-4-methoxy-l-phenylalanine residue by a biopterin-dependent hydroxylase Pep10, an O-methyltransferase Pep9, and a flavin-dependent halogenase Pep1. The biosynthetic research and heterologous expression system in this study set the stage for pathway engineering for more pepticinnamins generation in the future.

Discovery of a Phenylamine-Incorporated Angucyclinone from Marine Streptomyces sp. PKU-MA00218 and Generation of Derivatives with Phenylamine Analogues.

A new phenylamine-incorporated angucyclinone (1) featuring a unique 1-phenylbenzo[ cd]indol-3(1 H)-one moiety was discovered from marine Streptomyces sp. PKU-MA00218. A series of experimental investigations identified that 1 was produced from the nonenzymatic conversion of a C-ring-cleaved angucyclinone (2) with phenylamine. Utilizing the nonenzymatic conversion, 18 phenylamine-incorporated angucyclinone derivatives with halogen, methyl, methoxy, and carboxy substitutions were efficiently generated under mild conditions. These results highlighted the impressive roles of nonenzymatic reactions in expanding the structural diversity of angucyclinones.