Methyltransferase Domain-Focused Genome Mining for Fungal Polyketide Synthases.

A comparison of substrate-binding site amino acid residues in the C-methyltransferase (MT) domains of fungal nonreducing polyketide synthases (NR-PKSs) suggests that these residues are correlated with the methylation modes used by the PKSs. A PKS, designated as AsbPKS, with substrate-binding site residues distinct from those of other known PKSs is focused on. The characterization of AsbPKS revealed that it yields an isocoumarin derivative, anhydrosclerotinin B (1), the biosynthesis of which involves a previously unreported methylation pattern. This study demonstrates the utility of MT domain-focused genome mining for the discovery of PKSs with new functions.

Global genome mining-driven discovery of an unusual biosynthetic logic for fungal polyketide-terpenoid hybrids.

Genome mining has facilitated the efficient discovery of untapped natural products. We performed global genome mining in fungi and discovered a series of biosynthetic gene clusters (BGCs) that appeared to afford polyketide-terpenoid hybrids via a distinct biosynthetic mechanism from those adopted by known pathways. Characterization of one of the BGCs revealed that it yields the drimane-phthalide hybrid 1. During the biosynthesis of 1, the farnesyl group is unusually introduced by the dimethylallyltryptophan synthase-type prenyltransferase MfmD and is then cyclized by the Pyr4-family terpene cyclase MfmH. The replacement of MfmH with its homologue OcdTC gave another hybrid molecule with a monocyclic terpenoid moiety. Moreover, PsetPT, an MfmD homologue, was found to perform dimethylallylation and was then engineered to install a geranyl group. Our study unraveled an unusual biosynthetic mechanism for fungal phthalide-terpenoid hybrids and provided insights into how their structural diversification could be achieved.

Genomics-driven derivatization of the bioactive fungal sesterterpenoid variecolin: Creation of an unnatural analogue with improved anticancer properties.

A biosynthetic gene cluster for the bioactive fungal sesterterpenoids variecolin (1) and variecolactone (2) was identified in Aspergillus aculeatus ATCC 16872. Heterologous production of 1 and 2 was achieved in Aspergillus oryzae by expressing the sesterterpene synthase VrcA and the cytochrome P450 VrcB. Intriguingly, the replacement of VrcB with homologous P450s from other fungal terpenoid pathways yielded three new variecolin analogues (5-7). Analysis of the compounds' anticancer activity in vitro and in vivo revealed that although 5 and 1 had comparable activities, 5 was associated with significantly reduced toxic side effects in cancer-bearing mice, indicating its potentially broader therapeutic window. Our study describes the first tests of variecolin and its analogues in animals and demonstrates the utility of synthetic biology for creating molecules with improved biological activities.

Biosynthetic Elucidation and Structural Revision of Brevione†E: Characterization of the Key Dioxygenase for Pathway Branching from Setosusin Biosynthesis.

Brevione E (1) is a fungal hexacyclic meroditerpenoid with unique oxepane and cycloheptenone moieties. In this study, we identified the biosynthetic gene cluster of 1 and elucidated its biosynthetic pathway via heterologous expression of the biosynthetic genes and in vitro enzymatic reactions. Surprisingly, reexamination of the structure of 1 revealed a substituted tetrahydrofuran ring instead of the previously proposed oxepane system. Moreover, we determined that cycloheptenone synthesis involves skeletal rearrangement catalyzed by the α-ketoglutarate-dependent dioxygenase BrvJ. BrvJ is highly homologous to SetK, which engages in the biosynthesis of another fungal metabolite, setosusin, and accepts the same substrate as BrvJ but performs only simple hydroxylation. Finally, we identified the key amino acid residues critical for product selectivity of BrvJ and SetK, providing insight into how the biosynthesis pathways of 1 and setosusin diverge and how fungi diversify natural products.

A qualitative study of facilitators and barriers to nurses' innovation at work.

AIM: This article describes innovative experiences of nurses during clinical work and identifies the factors promoting and hindering clinical innovation. BACKGROUND: The nursing staff is replete with innovations in providing medical and healthcare that can help nurses solve clinical problems. Nurses need to understand their experiences in the creation and identify the factors that facilitate or hinder clinical innovation. METHODS: A semi-structured interview question framework was used to explore nurses' innovation patents, particularly the development of innovative ideas and the difficulties encountered in innovation. From 15 December 2021 to 17 February 2022, 14 nurses with innovation experiences were recruited in Shanghai, China, using a snowball sampling method. Interviews were conducted in the participants' native language, Chinese, and the interview records were analysed using Colaizzi phenomenological analysis. RESULTS: This study has formed three main themes which are facilitators (including seven sub-themes), barriers (including two sub-themes) and results of the innovation. Position characteristics, the ability to resolve obstacles in clinical work, peer motivation and pressure urge nurses to have innovative ideas. Self-support and external support helped nurses overcome difficulties in the process of innovation. Technical translation and seeking professional assistance help realize innovative ideas for nurses. However, busy clinical work and limited resources are important barriers to nurse innovation. CONCLUSION: Innovation in nursing comes from clinical problems, and nurses' creativity in healthcare organizations can promote positive changes in nursing practice. Nurses have carried out many innovative activities during their work, including quite a few aspects of promotion in this process. Some factors have hindered or promoted this innovation process, which is more extensive than in previous studies. Therefore, policymakers, nurse educators and hospital managers should establish an environment conducive to innovation and provide nurses with job flexibility and resources to foster innovation. IMPLICATIONS FOR NURSING MANAGEMENT: This study suggests that nursing managers should take the initiative to care for nurses, pay attention to their contributions to hospitals and provide them with abundant resources. In addition, managers should try their best to allow every nurse to participate in exchanges and learn continuously. In doing so, the innovation level of nurses can be greatly improved.

Molecular and Computational Bases for Spirofuranone Formation in Setosusin Biosynthesis.

The 3(2H)-furanone unit is observed in many biologically active natural products, as represented by the antifungal medication griseofulvin. Setosusin (1) is a fungal meroditerpenoid featuring a unique spiro-fused 3(2H)-furanone moiety; however, the biosynthetic basis for spirofuranone formation has not been investigated since its isolation. Therefore, in this study we identified the biosynthetic gene cluster of 1 in the fungus Aspergillus duricaulis CBS 481.65 and elucidated its biosynthetic pathway by heterologous reconstitution of related enzyme activities in Aspergillus oryzae. To understand the reaction mechanism to afford spirofuranone, we subsequently performed a series of in vivo and in vitro isotope-incorporation experiments and theoretical calculations. The results indicated that SetF, the cytochrome P450 enzyme that is critical for spirofuranone synthesis, not only performs the epoxidation of the polyketide portion of the substrate but also facilitates the protonation-initiated structural rearrangement to yield 1. Finally, a mutagenesis experiment using SetF identified Lys303 as one of the potential catalytic residues that are important for spirofuranone synthesis.

Genome Mining-Driven Discovery of 5-Methylorsellinate-Derived Meroterpenoids from Aspergillus funiculosus.

Heterologous expression of a cryptic gene cluster in the fungus Aspergillus funiculosus CBS 116.56 led to the discovery of four new meroterpenoids, funiculolides A-D (1-4), derived from the aromatic polyketide 5-methylorsellinic acid (5-MOA). Intriguingly, funiculolide D (4), the apparent end product of the pathway, harbors an unusual spirocyclopentanone moiety, which is synthesized by the oxidative rearrangement catalyzed by the ferrous iron and α-ketoglutarate-dependent dioxygenase FncG.

Heterologous Biosynthesis of Tetrahydroxanthone Dimers: Determination of Key Factors for Selective or Divergent Synthesis.

Tetrahydroxanthone dimers are fungal products, among which secalonic acid D (1) is one of the most studied compounds because of its potent biological activity. Because the biosynthetic gene cluster of 1 has been previously identified, we sought to heterologously produce 1 in Aspergillus oryzae by expressing the relevant biosynthetic genes. However, our initial attempt of the total biosynthesis of 1 failed; instead, it produced four isomers of 1 due to the activity of an endogenous enzyme of A. oryzae. Subsequent overexpression of the Baeyer-Villiger monooxygenase, AacuH, which competes with the endogenous enzyme, altered the product profile and successfully generated 1. Characterization of the key biosynthetic enzymes revealed the surprising substrate promiscuity of the dimerizing enzyme, AacuE, and indicated that efficient synthesis of 1 requires highly selective preparation of the tetrahydroxanthone monomer, which is apparently controlled by AacuH. This study facilitates engineered biosynthesis of tetrahydroxanthone dimers both in a selective and divergent manner.

Nurses' intention to stay: The impact of perceived organizational support, job control and job satisfaction.

AIM: To propose a theoretical model of intention to stay (ITS) and examine the effects of perceived organizational support, job control and job satisfaction on ITS. DESIGN: Cross-sectional multicentre survey. METHODS: The survey was conducted from January 2017-July 2017 and comprised 3,240 clinical nurses from nine tertiary hospitals in eastern, central and western China, with 2,352 effective responses. Structural equation modelling was used to analyse the relationship between ITS and its correlative factors. RESULTS: The hypothesized model was supported. Job control, perceived organizational support and job satisfaction significantly and directly affected nurses' ITS. Furthermore, job control and perceived organizational support showed indirect effects on ITS, which was mediated by job satisfaction. Perceived organizational support could positively influence job control to have a further impact on job satisfaction and ITS. CONCLUSION: Based on a large sample of Chinese tertiary hospital nurses, this study proposed and verified a theoretical model of nurses' ITS, revealing that organization characteristics, work characteristics and affective response to work can have an impact on ITS. IMPACT: This study was the first to examine the relationships among perceived organizational support, job control, job satisfaction and ITS, enriching the theoretical model of ITS. Nurse managers can improve nurses' ITS by enhancing their perceived organizational support, job control and job satisfaction.

The relationship between psychological capital and innovation behaviour in Chinese nurses.

AIM: To explore the serial-multiple mediation of job control and perceived organisational innovation climate between psychological capital and innovation behaviour among Chinese nurses through structural equation modelling. BACKGROUND: Nurses' innovation not only promotes the development of the nursing industry but also improves the quality of care and promotes patient prognosis. Thus, it is essential to clarify the factors affecting nurses' innovative behaviour and to provide a theoretical basis for improving nurses' innovative behaviour. METHODS: A cross-sectional study was conducted among 4,677 Chinese nurses from 18 hospitals. The PCQ-R, Nurses' Job Control Scale, the Nurses' Organizational Innovation Climate Scale, and the Nurses' Innovation Behaviour Scale were used to conduct a questionnaire survey. RESULTS: According to the serial-multiple mediation, the mediating role of job control and perceived organisational innovation climate between psychological capital and innovative behaviour is significant. (Z = 7.25, p < .05). CONCLUSIONS: Higher psychological capital can promote nurses' innovation behaviour. Therefore, improving psychological capital can enhance the innovation behaviour of nurses. IMPLICATIONS FOR NURSING MANAGEMENT: It is essential to change hospital working environments for enhancing the innovation behaviour of health professionals. Managers could promote nurses' innovative behaviour by strengthening nurses' psychological capital.

Termipaniculatones A-F, chalcone-flavonone heterodimers from Terminthia paniculata, and their protective effects on hyperuricemia and acute gouty arthritis.

Terminthia paniculata (Sanyeqi) is widely used for treating inflammation and rheumatic arthritis in the folk areas of Yunnan province, China. Its total extract was first revealed with xanthine oxidase (XO) inhibitory activity in vitro and anti-hyperuricemic effect in vivo. Bioassay-guided separation on Fr. A5 yielded six chalcone-flavonone heterodimers, termipaniculatones A-F. Their structures were elucidated based on extensive spectroscopic analyses involving HRESIMS, 1D and 2D NMR, UV, IR and [α]D, and the absolute configuration of termipaniculatone F was verified by ECD calculation. Termipaniculatones A and E showed obvious XO inhibitory activity with IC50 values of 55.6 and 89.5 µM, respectively, which took effects via a mix-type mode. A molecular modeling study revealed that termipaniculatone A was well located into the active site of XO by interacting with Glu802, Arg880, Thr1010 and Val1011 residues. Termipaniculatone A showed anti-hyperuricemic effects by decreasing serum uric acid levels and inhibiting XO activity in both serum and liver on potassium oxonate (PO)-induced hyperuricemia mice, and anti-inflammatory activity through alleviating paw swelling on monosodium urate (MSU)-induced mice, at the concentration of 20 mg/kg. This is the first time to reveal the anti-hyperuricemic and anti-acute gouty arthritis potency of T. paniculata and the characteristic biflavonoids as active constituents, which provides valuable information for searching new XO inhibitors from natural sources.

Synthesis and biological evaluation of magnolol derivatives as melatonergic receptor agonists with potential use in depression.

Depression is associated with high mortality and morbidity rates worldwide. By our random screening, it was first revealed that 23 magnolol derivatives were synthesized followed by in vitro and in vivo evaluation of their antidepressive potential. Compound 7c was found to be the most promising compound, with EC50 values of 396.5 and 383.0 µM agitating on MT1 and MT2 receptors, respectively. Additionally, we carried out in vivo experiments to confirm the efficacy and safety of compound 7c; the compound was found to be orally bioavailable and highly effective, leading to a significant reduction of immobility time in a mouse model of depression (forced swimming test and tail suspension test); the acting mechanism was explored by determining its effect on the levels of monoamine neurotransmitters and their metabolites in different mice brain regions; the acute toxicity study showed that the 50% lethal dose (LD50) of 7c was higher than 2000 mg/kg, p. o. A total of 25 metabolites of 7c were identified, including 5 metabolites in phase I and 20 metabolites in phase II. Altogether, these results indicate that magnolol derivative 7c is a promising lead compound for the development of a new chemical class of antidepressant drugs.

LC-MS guided isolation of diterpenoids from Sapium insigne with α-glucosidase inhibitory activities.

Ten new (1-10) and ten known (11-20) diterpenoids involving ent-atisane, ent-seco-atisane, ent-kaurane and ent-seco-kaurane types were isolated from Sapium insigne under the guidance of LCMS-IT-TOF analyses. Their structures were characterized by extensive spectroscopic analyses (HRESIMS, UV, IR, 1D and 2D NMR). A putative biosynthetic pathway was proposed for ent-seco-atisane diterpenoids. Their inhibitory activities on α-glucosidase in vitro were tested for the first time. Compound 4 showed moderate inhibitory effect on α-glucosidase with an IC50 value of 0.34 mM via a noncompetitive inhibition mechanism (Ki = 0.27 mM). The preliminary structure-activity relationships of the ent-atisane diterpenoids inhibiting α-glucosidase were discussed.