The transcription factor MdBPC2 alters apple growth and promotes dwarfing by regulating auxin biosynthesis.

Auxin plays important roles throughout plant growth and development. However, the mechanisms of auxin regulation of plant structure are poorly understood. In this study, we identified a transcription factor (TF) of the BARLEY B RECOMBINANT/BASIC PENTACYSTEINE (BBR/BPC) family in apple (Malus × domestica), MdBPC2. It was highly expressed in dwarfing rootstocks, and it negatively regulated auxin biosynthesis. Overexpression of MdBPC2 in apple decreased plant height, altered leaf morphology, and inhibited root system development. These phenotypes were due to reduced auxin levels and were restored reversed after exogenous indole acetic acid (IAA) treatment. Silencing of MdBPC2 alone had no obvious phenotypic effect, while silencing both Class I and Class II BPCs in apple significantly increased auxin content in plants. Biochemical analysis demonstrated that MdBPC2 directly bound to the GAGA-rich element in the promoters of the auxin synthesis genes MdYUC2a and MdYUC6b, inhibiting their transcription and reducing auxin accumulation in MdBPC2 overexpression lines. Further studies established that MdBPC2 interacted with the polycomb group (PcG) protein LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) to inhibit MdYUC2a and MdYUC6b expression via methylation of histone 3 lysine 27 (H3K27me3). Silencing MdLHP1 reversed the negative effect of MdBPC2 on auxin accumulation. Our results reveal a dwarfing mechanism in perennial woody plants involving control of auxin biosynthesis by a BPC transcription factor, suggesting its use for genetic improvement of apple rootstock.

Calcyclin-binding protein-promoted degradation of MdFRUCTOKINASE2 regulates sugar homeostasis in apple.

Fructokinase (FRK) activates fructose through phosphorylation, which sends the activated fructose into primary metabolism and regulates fructose signaling capabilities in plants. The apple (Malus × domestica) FRK gene MdFRK2 shows especially high affinity to fructose, and its overexpression decreases fructose levels in the leaves of young plants. However, in the current study of mature plants, fruits of transgenic apple trees overexpressing MdFRK2 accumulated a higher level of fructose than wild-type (WT) fruits (at both young and mature stages). Transgenic apple trees with high mRNA MdFRK2 expression showed no significant differences in MdFRK2 protein abundance or FRK enzyme activity compared to WT in mature leaves, young fruits, and mature fruits. Immunoprecipitation-mass spectrometry analysis identified an skp1, cullin, F-box (SCF) E3 ubiquitin ligase, calcyclin-binding protein (CacyBP), that interacted with MdFRK2. RNA-sequencing analysis provided evidence for ubiquitin-mediated post-transcriptional regulation of MdFRK2 protein for the maintenance of fructose homeostasis in mature leaves and fruits. Further analyses suggested an MdCacyBP-MdFRK2 regulatory module, in which MdCacyBP interacts with and ubiquitinates MdFRK2 to facilitate its degradation by the 26S proteasome, thus decreasing the FRK enzyme activity to elevate fructose concentration in transgenic apple trees. This result uncovered an important mechanism underlying plant fructose homeostasis in different organs through regulating the MdFRK2 protein level via ubiquitination and degradation. Our study provides usable data for the future improvement of apple flavor and expands our understanding of the molecular mechanisms underlying plant fructose content and signaling regulation.

Early use of PCSK9 inhibitors in the prognosis of patients with acute coronary syndrome by protecting vascular endothelial function.

INTRODUCTION: Proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) has a protective effect on acute coronary syndrome (ACS). However, most studies have shown that this protective effect is based on a decrease in low-density lipoprotein cholesterol (LDL-C), while other mechanisms remain limited. This study aimed to determine whether PCSK9i can improve the prognosis of ACS patients by protecting endothelial function. METHODS: A total of 113 ACS patients were enrolled and randomly assigned to PCSK9i group (PCSK9i combined with statins) and control group (statins only). Blood lipids and endothelial function indicators were measured and analyzed 6 weeks before and after treatment. The effect of PCSK9i on the expression and secretion of endothelial function indicators in vascular endothelial cells were studied by cell experiments. RESULTS: After 6 weeks of treatment, endothelial function indicators such as NO, TM, ICAM-1, ET-1, and flow-mediated vasodilation (FMD) were significantly improved in PCSK9i group compared with control group. Only the changes of NO and vWF were associated with blood lipid levels, whereas the changes of other endothelial function indicators were not significantly associated with blood lipid levels. PCSK9i reduced the incidence of MACEs in patients with ACS compared to those in the control group. In cell experiments, PCSK9i treatment significantly ameliorated LPS induced endothelial injury in HUVECs. CONCLUSION: PCSK9i can protect vascular endothelial function partly independently of its lipid-lowering effect and ameliorate the prognosis of patients with ACS within 6 weeks. This mechanism may involve HSF1/HSPs related signaling pathways. Early use of PCSK9i in patients with ACS should be strongly considered in clinical practice.

Hypersensitive C-reactive protein as a potential indicator for predicting left ventricular hypertrophy in elderly community-dwelling patients with hypertension.

BACKGROUND: The aim of this study was to investigate the relationship between Hypersensitive C-reactive protein (hs-CRP) and left ventricular hypertrophy (LVH) in elderly community-dwelling patients with hypertension. METHODS: A cross-sectional study was conducted, involving the recruitment of 365 elderly hypertensive residents ≥ 65 years of age from five communities. The participants were divided into two groups: an LVH group (n = 134) and a non-LVH group (n = 231), based on the left ventricular mass index (LVMI) determined by echocardiography. Spearman correlation analysis was used to assess the relationship between hs-CRP and LVH. Univariate and Multivariate analysis was performed to detect variables associated with LVH. The diagnostic value of hs-CRP for LVH was expressed as the area under the receiver operating characteristic (ROC) curve. RESULTS: The incidence of LVH in elderly hypertension patients in the community was 36.7%. The hs-CRP levels were significantly higher in subjects with LVH compared to those without LVH (1.9 [0.8, 2.9] vs. 0.7 [0.4, 1.4], P = 0.002). Spearman correlation analysis demonstrated a positive correlation between hs-CRP and LVMI (r = 0.246, P < 0.001), as well as with IVST (r = 0.225, P < 0.001) and LVPWT (r = 0.172, P = 0.001). Among elderly hypertensive residents in the community, the cut-off value of hs-CRP for diagnosing LVH was 1.25 mg/L (sensitivity: 57.5%; specificity: 78.4%), and the area under the ROC curve for hs-CRP to predict LVH was 0.710 (95%CI: 0.654-0.766; P < 0.001). In the final model, hs-CRP ≥ 1.25 mg/L (OR = 3.569; 95%CI, 2.153-5.916; P<0.001) emerged as an independent risk factor for LVH. This association remained significant even after adjusting for various confounding factors (adjusted OR = 3.964; 95%CI, 2.323-6.765; P < 0.001). CONCLUSIONS: This community-based cohort of elderly hypertensive individuals demonstrates a strong association between hs-CRP levels and the presence of LVH. The hs-CRP ≥ 1.25 mg/L may serve as an independent predictor for LVH in hypertensive subjects and exhibit good diagnostic efficacy for LVH.

Review on the gentle hydrometallurgical treatment of WPCBs: Sustainable and selective gradient process for multiple valuable metals recovery.

The metal resource crisis and the inherent need for a low-carbon circular economy have driven the rapid development of e-waste recycling technology. High-value waste printed circuit boards (WPCBs) are an essential component of e-waste. However, WPCBs are considered hazardous to the ecosystem due to the presence of heavy metals and brominated organic polymers. Therefore, achieving the recycling of metals in WPCBs is not only a strategic requirement for building a green ecological civilization but also an essential guarantee for achieving a safe supply of mineral resources. This review systematically analyzes the hydrometallurgical technology of metals in WPCBs in recent years. Firstly, the different unit operations of pretreatment in the hydrometallurgical process, which contain disassembly, crushing, and pre-enrichment, were analyzed. Secondly, environmentally friendly hydrometallurgical leaching systems and high-value product regeneration technologies used in recent years to recover metals from WPCBs were evaluated. The leaching techniques, including cyanidation, halide, thiourea, and thiosulfate for precious metals, and inorganic acid, organic acid, and other leaching methods for base metals such as copper and nickel in WPCBs, were outlined, and the leaching performance and greenness of each leaching system were summarized and analyzed. Eventually, based on the advantages of each leaching system and the differences in chemical properties of metals in WPCBs, an integrated and multi-gradient green process for the recovery of WPCBs was proposed, which provides a sustainable pathway for the recovery of metals in WPCBs. This paper provides a reference for realizing the gradient hydrometallurgical recovery of metals from WPCBs to promote the recycling metal resources.

Cu(I)/Ionic Liquids Promote the Conversion of Carbon Dioxide into Oxazolidinones at Room Temperature.

Recently, the efficient chemical fixation of carbon dioxide (CO2) into high value chemicals without using noble metal catalysts has become extremely appealing from the viewpoint of sustainable chemistry. In this work, a one-pot three component reaction of propargylic alcohols, anines and CO2 that can proceed in an atom economy and environmentally benign manner by combination of CuI and tetrabutylphosphonium imidazol ([P4444][Im]) as a catalyst was described. Catalysis studies indicate that this catalytic system is an effective catalyst for the conversion of CO2 into oxazolidinones at room temperature and ambient pressure without any solvent. The results provide a useful way to design novel noble metal-free catalyst systems for the transformation of CO2 into other valuable compounds.

PCSK9 inhibitors ameliorate arterial stiffness in ACS patients: evidences from Mendelian randomization, a retrospective study and basic experiments.

Background: Current evidences suggest that Proprotein Convertase Subtilisin/kexin Type 9 inhibitors (PCSK9i) exhibit a protective influence on acute coronary syndrome (ACS). Nevertheless, further investigation is required to comprehend the impact and mechanisms of these pharmaceutical agents on inflammatory factors and arterial stiffness (AS) in patients with ACS. Consequently, the objective of this study is to ascertain the influence of PCSK9i on arterial stiffness in ACS patients and elucidate the underlying mechanisms behind their actions. Methods: This study employed Mendelian randomization (MR) analysis to examine the association between genetic prediction of PCSK9 inhibition and arterial stiffness. Data of 71 patients with ACS were retrospectively collected, including PCSK9i group (n = 36, PCSK9 inhibitors combined with statins) and control group (n = 35, statins only). Blood lipid levels, inflammatory markers and pulse wave velocity (PWV) data were collected before treatment and at 1 and 6 months after treatment for analysis. Additionally, cell experiments were conducted to investigate the impact of PCSK9i on osteogenesis of vascular smooth muscle cells (VSMCs), utilizing western blot (WB), enzyme-linked immunosorbent assay (ELISA), and calcification index measurements. Results: The results of the MR analysis suggest that genetic prediction of PCSK9 inhibition has potential to reduce the PWV. Following treatment of statins combined with PCSK9 inhibitors for 1 and 6 months, the PCSK9i group exhibited significantly lower levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), C-reactive protein (CRP), interleukin-6 (IL-6), fibrinogen (FIB) and procalcitonin (PCT) compared to the control group (p < 0.05). Additionally, PWV in the PCSK9i group demonstrated significant reduction after 6 months of treatment and was found to be associated with the circulating CRP level. In cell experiments, PCSK9i pretreatment ameliorated osteogenesis of VSMCs through reducing the deposition of calcium ions, alkaline phosphatase (ALP) activity, and expression of runt-related transcription factor 2 (RUNX2). Conclusion: PCSK9i have potential to enhance arterial stiffness in ACS patients. Specifically, at the clinical level, this impact may be attributed to alterations in circulating CRP levels. At the cellular level, it is associated with the signaling pathway linked to RUNX2.

miRNAs Influence m6A RNA Methylation through FTO and IGF2BP2 in Pressure Overload-Induced Heart Failure.

BACKGROUND: N6-adenosine methylation (m6A) is a prevalent RNA modification associated with heart failure, alongside aberrant miRNA expression. Despite indications of miRNAs regulating m6A modification, their specific influence on m6A in heart failure remains unclear. METHODS: The initial analysis utilized transcriptome and methylation sequencing data from GSE131296 in mice to identify key m6A methylation enzymes in heart failure and construct an associated network. Integration of miRNA sequencing data from GSE231700 revealed miRNAs influencing m6A methylation enzymes, contributing to the formation of a comprehensive network. Furthermore, differential miRNA levels in human serum were assessed via qPCR, and the expression of m6A methyltransferases in the heart was confirmed using proteomic databases. RESULTS: In pressure overload-induced heart failure mice, 217 mRNAs showed differential expression, with FTO and IGF2BP2 identified as m6A methylation enzymes. Subsequent methylation sequencing revealed 884 highly-methylated and 178 lowly-methylated peaks, establishing a network linking Fto and Igf2bp2 with these peaks. Additionally, miRNA sequencing identified 156 differentially expressed miRNAs, including let-7b-5p and miR-23b-3p, predicted as m6Aregulating miRNAs, both elevated in heart failure patients. CONCLUSION: miR-23b-3p and let-7b-5p are identified as potential regulators of RNA methylation in heart failure, acting via FTO and IGF2BP2, offering new insights into the role of miRNA-mediated RNA methylation and its potential therapeutic avenues for heart failure.

Axitinib targets cardiac fibrosis in pressure overload-induced heart failure through VEGFA-KDR pathway.

Background: There are no specific clinical medications that target cardiac fibrosis in heart failure (HF). Recent studies have shown that tyrosine kinase inhibitors (TKIs) may benefit fibrosis in various organs. However, there is limited research on their application in cardiac fibrosis. Axitinib, an FDA-approved tyrosine kinase inhibitor, was used to evaluate its effects on cardiac fibrosis and function in pressure overload-induced heart failure. Methods: To build a pharmacological network, the pharmacological targets of axitinib were first retrieved from databases and coupled with key heart failure gene molecules for analysis and prediction. To validate the results outlined above, 8-week-old male C57BL/6 J mice were orally administrated of axitinib (30 mg/kg) daily for 8 weeks after Transverse Aortic Constriction (TAC) surgery. Mouse cardiomyocytes and cardiac fibroblasts were used as cell lines to test the function and mechanism of axitinib. Results: We found that the pharmacological targets of axitinib could form a pharmacological network with key genes involved in heart failure. The VEGFA-KDR pathway was found to be closely related to the differential gene expression of human heart-derived primary cardiomyocyte cell lines treated with axitinib, based on analysis of the publicly available dataset. The outcomes of animal experiments demonstrated that axitinib therapy greatly reduced cardiac fibrosis and improved TAC-induced cardiac dysfunction. Further research has shown that the expression of transforming growth factor-ß(TGF-ß) and other fibrosis genes was significantly reduced in vivo and in vitro. Conclusion: Our study provides evidence for the repurposing of axitinib to combat cardiac fibrosis, and offers new insights into the treatment of patients with HF.

Mn(CeZr)Ox chelation-induced synthesis and its hydrothermal aging characteristics for catalytic abatement of toluene.

In this work, Mn(CeZr)Ox was synthesized by using chelation-induced synergistic self-assembly strategy for the combustion of toluene. The physicochemical properties of the synthesized catalysts were characterized by XRD, ICP-MS, SEM, TEM, XPS and N2 sorption. The Mn(CeZr)Ox catalyst with T90 = 225 °C exhibited improved catalytic performance than the original MnOx catalyst (T90 = 260 °C) and had significant low-temperature activity. The relationship between catalyst activity and structure was analyzed. By substituting Ce and Zr elements into the hollow microspheres of MnO2, oxygen vacancies were produced. The main factors affecting the catalytic activity of the catalyst and the reason why it remained high catalytic activity after a long period of hydrothermal treatment were discussed. After hydrothermal aging, the original pore structure of Mn(CeZr)Ox catalyst collapsed and the specific surface area decreased, but the overall crystallinity of the catalyst increased and the content of oxygen species in the lattice increased. The distribution of Mn and oxygen species on the catalyst surface changed significantly after hydrothermal treatment. The appropriate ratio of Mn4+ to Mn3+ and the ratio of lattice oxygen to adsorbed oxygen species are beneficial to the redox reaction cycle.

Effects of circular RNA Ttc3/miR-148a/Rcan2 axis on inflammation and oxidative stress in rats with acute kidney injury induced by sepsis.

Aim Increasing evidence demonstrated circular RNAs (circRNAs) are involved in the development of various diseases, including sepsis-induced AKI. Although CIRC-Ttc3 has been proved to regulate cardiac function after myocardial infarction, its role in sepsis-induced AKI remains unclear. MATERIALS AND METHODS: The AKI rat model was firstly induced by sepsis through cecal ligation puncture (CLP). Serum levels of creatinine, BUN, NGAL, TNF-α, IL-6, SOD, MDA and IL-1ß were measured through appropriate kits. The pathological alteration and renal microvascular permeability in renal tissues were determined by HE staining and Evans Blue assays. Cell apoptosis was detected by TUNEL assay. The expression levels of CIRC-Ttc3, miR-148a, TNF-α, IL-1ß and iNOS in rats' renal samples were tested by qRT-PCR or/and western blot. The binding ability between CIRC-Ttc3 and miR-148a was evaluated through luciferase reporter, RIP and RNA pull-down assays. KEY FINDINGS: Kidney injury was found in CLP-treated rats. CIRC-Ttc3 expression was down-regulated, and upregulation of CIRC-Ttc3 improved inflammatory responses and oxidative stress in AKI rats. Mechanismly, CIRC-Ttc3 was confirmed to bind to and negatively regulate miR-148a. Further rescue assays revealed that overexpression of miR-148a rescued the improvement of CIRC-Ttc3 on sepsis-induced AKI. Then, it was illustrated that CIRC-Ttc3 regulated Rcan2 expression by binding to miR-148a. Finally, knockdown of Rcan2 reversed the effects of miR-148a inhibition on sepsis-induced AKI. SIGNIFICANCE: CIRC-Ttc3 relieved inflammation and oxidative stress through regulating the miR-148a/Rcan2 axis in rats with AKI induced by sepsis. Therefore, CIRC-Ttc3 may be a potential therapeutic target for sepsis-induced AKI.

Facile synthesis of Pt-Ce0.63Zr0·37O2-Y catalysts and the application in catalytic oxidation of toluene.

In this work, a series of Pt-Ce0.63Zr0·37O2-Y catalysts were prepared by unique simple mechanical mixing method. The catalytic activity of these catalysts for toluene oxidation was investigated. The physicochemical properties of the catalysts were characterized by XRD, ICP-MS, SEM, TEM, XPS and N2 sorption. Pore size distribution was analyzed according nitrogen adsorption and desorption isotherms. The catalytic results showed that using NaY as support for Pt-Ce0.63Zr0·37O2-Y could enhance the conversion of toluene during the oxidation process in comparison with HY. Further mixing cerium zirconium solid solution with Pt-NaY can improve the oxidation catalytic property of these catalysts. The conversion of toluene over Pt-Ce0.63Zr0·37O2-NaY reached more than 90% at 200 °C. High catalytic stability was obtained for toluene oxidation over Pt-Ce0.63Zr0·37O2-NaY. Platinum, cerium and zirconium can be uniformly dispersed on Y zeolite with small particle size by simple mechanical synthesis. The effect of drying methods on catalytic activity and hydrothermal stability of catalysts were also investigated in this research.

Gender context modulation on the self-enhancement effect of vocal attractiveness evaluation.

People evaluated their own voices as sounding more attractive than others rated their voices (i.e., self-enhancement effect from the perspective of the rater, termed "SE_rater"), and people also rated their own voices as more attractive than the voices of others (i.e., self-enhancement effect from the perspective of the voice, termed "SE_voice"). The aim of the present study is to explore whether the gender context (i.e., same-sex and opposite-sex rating context) could influence the SE effect of voice attractiveness evaluation. Male and female participants were asked to rate the attractiveness of their own voices and other participants' voices, either in a same-sex session or an opposite-sex session. The results demonstrated both the SE_rater and SE_voice effect in the same-sex and opposite-sex contexts, for both male and female. More importantly, we found that the SE_rater for the male voices was significantly greater than that for the female voices in the same-sex context whereas no such difference was found in the opposite-sex context. In addition, the SE_voice effect in men was larger in the same-sex context than that in the opposite-sex context whereas the SE_voice in women was smaller in the same-sex context than that in the opposite-sex context. These findings indicated that the self-enhancement effect of vocal attractiveness was modulated by the gender context.

Molecular Mechanism of HSF1-Upregulated ALDH2 by PKC in Ameliorating Pressure Overload-Induced Heart Failure in Mice.

Evidences abound that HSF1 and ALDH2 are of cardioprotective effect, yet there is still no report on whether HSF1 can regulate ALDH2 to delay the occurrence of heart failure. We first established the pressure overload-induced heart failure model of mice by transverse aortic constriction (TAC) and discovered that, in the forming period of heart failure, changes of HSF1 and ALDH2 expression recorded the consistent trend. When HSF1 was upregulated/downregulated to delay/promote the occurrence of heart failure, PKC and ALDH2 also showed increased/decreased expression. And when ALDH2 was upregulated/downregulated, the role of HSF1 in delaying the occurrence of heart failure strengthened/weakened. Next, we used mechanical stretch to establish a pressure-stimulated myocardial hypertrophy model and discovered an increased expression of both HSF1 and ALDH2. When HSF1 was upregulated/downregulated to increase/decrease the expression of myocardial hypertrophy gene beta-MHC, PKC and ALDH2 recorded an increased/decreased expression. When an inhibitor was used to downregulate the expression of PKC in cardiomyocytes, we found that the role of HSF1 in upregulating ALDH2 beta-MHC weakened. These findings suggest that HSF1 can upregulate the expression of ALDH2 via PKC to promote pressure-stimulated myocardial compensatory hypertrophy, which is an important molecular pathway for HSF1 to ameliorate heart failure.

Facile synthesis of Co-Fe-B-P nanochains as an efficient bifunctional electrocatalyst for overall water-splitting.

Design of cost-effective bifunctional electrocatalysts for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital for developing hydrogen energy for the future. Herein, a cost-effective phosphorus-doped Co-Fe-B material with chain-like structure (denoted as Co1-Fe1-B-P) is reported as an efficient and novel bifunctional electrocatalyst for the OER and HER, and was produced via a facile water-bath synthesis and subsequent phosphorization. For the OER, the as-prepared Co1-Fe1-B-P nanochains require an extremely low overpotential of about 225 mV at 10 mA cm-2 and possess a small Tafel slope of 40 mV dec-1 in alkaline media. Impressively, the HER properties of Co1-Fe1-B-P nanochains are superior to those of P-free Co-Fe-B in terms of overpotential at 10 mA cm-2 (173 mV vs. 239 mV) and kinetic Tafel slope (96 mV dec-1vs. 105 mV dec-1). The synergetic effect between Co-Fe-B and doped-P is mainly responsible for the satisfactory bifunctional performance, while the one-dimensional (1D) chain-like structure endows Co1-Fe1-B-P with abundant catalytically active sites that enhance the atom utilization efficiency. Moreover, the developed Co1-Fe1-B-P nanochains can be simultaneously utilized as both the cathode and anode for overall water-splitting, which requires a cell voltage of only 1.68 V to deliver 10 mA cm-2. This work provides a feasible and promising protocol to realize metal borides as efficient electrocatalysts in energy-related applications.

Simultaneous removal of Hg0 and H2S at a high space velocity by water-resistant SnO2/carbon aerogel.

A seaweed-templated pathway was developed for the controllable synthesis of SnO2/carbon aerogel for the simultaneous removal of Hg0 and H2S in natural gases, where the SnO2 nanoparticles with an outer diameter of 4-20 nm were highly dispersed and conjoined by graphitic carbon, forming a 3D core-shell structure with a developed pore network. The synthesized sorbent performed a complete removal of Hg0 and H2S at a high space velocity of 70,000 h-1 and showed resistance to water. At 5% breakthrough, the Hg0 and H2S capture capacities reached as high as 10.37 mg g-1 and 392.23 mg g-1, respectively, which are much higher than those of the existing commercial sorbents. More importantly, the spent sorbent could be easily regenerated without significant performance degradation over five cycles. The 3D interconnected macro- and mesopores are beneficial for the Hg0 and H2S removal at a high space velocity, and the core-shell structure is conducive to prevent poisoning from water. The Hg0 and H2S removal over the SnO2/aerogel conforms to the E-R mechanism, where H2S is first adsorbed and dissociated on the SnO2 surface to produce active sulfur species, and the adsorbed sulfur then reacts with gaseous Hg0 to form HgS.

The folding dynamics and infrared spectra of a photocleaved tetrapeptide predicted by theoretical simulations.

We present the theoretical investigation of the folding dynamics of a photocleaved tetrapeptide with a disulfide bridge by using combined semiempirical quantum-mechanical and molecular-mechanical molecular dynamics simulations and high-leveled CASPT2//CASSCF/Amber calculations. We find that in acetonitrile solvent, aside from the recombination of the sulfur biradicals, the peptide can refold to a double sulfur-heterocyclic ring structure or a fully opened structure. The radical bicyclization reaction and the intramolecular hydrogen transfer are responsible for the low recombination rate of the cysteinyl radicals, respectively. On the other hand, in methanol solvent, the formation of the solvent cages around the sulfur radicals reduces the possibility of the close contact of the radicals. The calculated infrared spectra of the amide I mode corresponding to the conformation changes of the peptide can well explain the experimental observation.