Increased yield of 2-O-α-d-glucopyranosyl-l-ascorbic acid synthesis by α-glucosidase using rational design that regulating the ground state of enzyme and substrate complex.

BACKGROUND: α-Glucosidase (AG) is a bifunctional enzyme, it has a capacity to synthesize 2-O-α-d-glucopyranosyl-l-ascorbic acid (AA-2G) from l-ascorbic acid (L-AA) and low-cost maltose under mild conditions, but it can also hydrolyze AA-2G, which leads to low synthesis efficiency of AA-2G. MAIN METHODS AND MAJOR RESULTS: This study introduces a rational molecular design strategy to regulate enzymatic reactions based on inhibiting the formation of ground state of enzyme-substrate complex. Y215 was analyzed as the key amino acid site affecting the affinity of AG to AA-2G and L-AA. For the purpose of reducing the hydrolysis efficiency of AA-2G, the mutant Y215W was obtained by analyzing the molecular docking binding energy and hydrogen bond formation between AG and the substrates. Compared with the wild-type, isothermal titration calorimetry (ITC) results showed that the equilibrium dissociation constant (KD ) of the mutant for AA-2G was doubled; the Michaelis constant (Km ) for AA-2G was reduced by 1.15 times; and the yield of synthetic AA-2G was increased by 39%. CONCLUSIONS AND IMPLICATIONS: Our work also provides a new reference strategy for the molecular modification of multifunctional enzymes and other enzymes in cascade reactions system.

Development and Application of Global Health Events-Mental Stress Scale for Assessment of Medical Staff's Acute Mental Stress Responses.

Background: Medical workers have been increasingly involved in emergent public health events, which can lead to severe stress. However, no standardized, officially recognized, unified tool exists for mental distress measurement in medical workers who experienced the public health events. Purpose: In the present study, we propose the Global Health Events-Mental Stress Scale (GHE-MSS), as a revised version of the Impact of Event Scale-Revision (IES-R), for assessment of medical workers' acute mental stress responses within one month and their chronic mental stress responses within six months after major health events. Patients and methods: The IES-R was slightly modified, developed, and its reliability and validity were tested using the Delphi survey, primary survey with 115 participants, formal survey with 300 participants, and clinical evaluation with 566 participants. Results: Exploratory factor analysis and confirmatory factor analysis confirmed a promising validity of the scale. The values of Cronbach's alpha coefficient, the Spearman-Brown coefficient, and the retested Cronbach's alpha coefficient of the scale applied for the clinical evaluation were 0.88, 0.87, and 0.98, respectively, which confirmed a good internal consistency and stability. The results of the goodness-of-fit test indicated a good adaptation of the model. A correlation analysis was conducted to assess the correlation between the GHE-MSS and the PCL-C, which had a correlation coefficient of 0.68 (P<0.01). Conclusion: GHE-MSS can be applied with a promising reliability and validity for the assessment of the acute mental stress response of medical workers experiencing public health events. This method can also be used for the screening of mental stress-associated disorders.

Near-infrared reflectance spectroscopy-based fast versicolorin A detection in maize for early aflatoxin warning and safety sorting.

Aflatoxins (AFs) are potent carcinogens present in numerous crops. Access to accurate methods for evaluating contamination is a critical factor in aflatoxin risk assessment. Versicolorin A (Ver A), a precursor of aflatoxin B1 (AFB1), can be used as an indicator for the presence of AFB1, even when the AF is not yet detectable. Currently employed Ver A detection methods are expensive, time consuming, and difficult to apply to numerous samples. Herein, Ver A was detected via near-infrared spectroscopy. Both quantitative and two-grade sorting methods were set-up using the extreme gradient boosting algorithm coupled with a support vector machine. This two-tiered method obtained a root-mean-square error of prediction value of 3.57 µg/kg for the quantitative model, and an accuracy rate of 90.32% for the sorting approach. This novel method is rapid, accurate, solvent free, requires no sample pretreatment, and detects Ver A in maize, making it convenient for practical use.

[Detection Rate of Central Nervous System Leukemia Can Be Improved by Cell Preservation Solution].

OBJECTIVE: To investigate whether cell preservation solution can prolong the survival time of leukemia cells and increase the survival rate, so as to improve the detection rate of central nervous system leukemia. METHODS: Kasumi cells were added into cerebrospinal fluid (CSF) supernatant with or without cell preservation solution to compare cell viability and biological characteristics at different time point. Wright Giemsa staining was used to compare cell morphology; cell counting, CCK-8 method, and trypan blue staining were used to compare the cell number, and flow cytometry was used to compare the cell viability. The expression of AML-ETO tumor fusion gene was detected by fluorescence quantitative RT-PCR. RESULTS: At different time points (8 h and 24 h), the survival, molecular biological characteristics and RT-PCR result of the cells in CSF with cell preservation solution were significantly better than those in normal cerebrospinal fluid. CONCLUSION: Cell preservation solution can effectively improve the survival time and survival rate of leukemic cells, thereby increase the detection rate of CNS leukemia.

Predictive model of aflatoxin contamination risk associated with granary-stored corn with versicolorin A monitoring and logistic regression.

Predictions of aflatoxin (AF) in grain at post-harvest can be useful for ensuring the safety of stored grain. Versicolorin (Ver) A, a precursor of AFB1, can serve as an early indicator of AF contamination, even when AFs themselves are present at undetectable levels. In the current research, we developed a probabilistic model based on logistic regression and Ver A levels to estimate the risk of AF contamination in stored corn. Moisture content, aflatoxigenic fungal load, and initial and maximum values of Ver A in the first three sampling cycles were experimentally determined as the four important factors for the probabilistic model. Both internal and external model validations were shown to be high at 96.4% and 93.3%, respectively. For high-risk samples, a precise model was developed to predict the maximum period of safe storage, which can be useful for decision-making by the stakeholders in feed and food supply chain. Our findings provide a basis tool for establishing an early warning system for AF contamination in granaries, which can improve global food safety.

[Appearance and clinical value of MRI in sinonasal embryonal rhabdomyosarcoma].

OBJECTIVE: To investigate the appearance and clinical value of MRI in the diagnosis of embryonal rhabdomyosarcoma in nasal cavity and paranasal sinuses. METHODS: The clinical, pathological and MRI findings of five patients with pathology proved embryonal rhabdomyosarcoma in nasal cavity and paranasal sinuses were retrospectively analyzed. RESULTS: The major clinical symptoms included nasal obstruction (4 cases), exophthalmus (4 cases), decreased eyesight (2 cases), epistaxis (1 case), decreased olfactory sensation (1 case) and restriction of eyeball movement (1 case). All 5 cases involved multi-location. Among them, 4 cases mainly located in the ethmoid sinus, one mainly located in the nasal septum. According to the IRS, 1 case was at stage II, the other 4 cases were at stage III. Compared to the grey matters, on T1 weighted image, the masses were homogenously isointensity in 2 cases, isointensity with patchy hyperintensity in 3 cases. On T2 weighted images, the masses were slightly hyperintensity with patchy hypointensity in 2 cases. Slightly hyperintensity with patchy hyperintensity in 3 cases. All 5 cases were markley heterogeneously enhanced after administration of contrast agents, with patchy of non-enhanced area. Of them, two were grape-like enhanced. Four cases presented with intratumor hemorrhage. Five with bony destruction. All of the 5 cases showed orbits and anterior cranial fossa meningeal involvement. CONCLUSIONS: There are some special MRI findings in embryonal rhabdomyosarcoma located in nasal cavity and paranasal sinuses. MRI can depict the encroachment of the tumor accurately, and may play an important role in clinical staging and in curative effect evaluation.