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The development of effective therapeutics against COVID‐19 requires a thorough understanding of the receptor recognition mechanism of the SARS‐CoV‐2 spike (S) protein. Here the multidomain collective dynamics on the trimer of the spike protein has been analyzed using normal mode analysis (NMA). A common nanomechanical profile was identified in the spike proteins of SARS‐CoV‐2 and its variants. The profile involves collective vibrations of the receptor‐binding domain (RBD) and the N‐terminal domain (NTD), which may mediate the physical interaction process. Quantitative analysis of the collective modes suggests a nanomechanical property involving large‐scale conformational changes, which explains the difference in receptor binding affinity among different variants. These results support the use of intrinsic global dynamics as a valuable perspective for studying the allosteric and functional mechanisms of the S protein. This approach also provides a low‐cost theoretical toolkit for screening potential pathogenic mutations and drug targets. [ABSTRACT FROM AUTHOR]

We introduce vibrational spectroscopy to quantitatively measure the phenotypic heterogeneity of senescent stem cells in the aging process at the single cell level. Using an aging model of serially passaged human mesenchymal stem cells (MSCs), we characterized the phenotypic changes of MSCs during different aged stages and discovered a stepwise aging process with several distinct subtypes. [ABSTRACT FROM AUTHOR]

Taking chitosan (CS) and soybean protein isolate (SPI) as composite membrane substrates and natural antioxidants as active substances, an edible active preservative film with inhibitory effect on lipid oxidation was developed. After optimizing the type and concentration of antioxidants through the mechanical properties, microstructure, physical properties, and antioxidant properties of the composite membrane, the preservation effect of the composite membrane on walnut oil was investigated. Results showed that, eight antioxidants significantly improved the oxygen-barrier ability of the composite membranes (P<0.05). Especially, the peroxide value of walnut oil was reduced by about 80% and maintained excellent mechanical properties with the addition of astaxanthin, grape seed extracts and vitamin C. When the addition of astaxanthin was 0.3%, the composite membrane exhibits the best performance, then the tensile strength, elongation at break, DPPH free radical scavenging capacity and water vapor permeability of the composite membrane were 6.546 MPa, 69.962%, 80.1%, 1.21 g⋅mm/m²⋅h⋅kPa, respectively. Scanning electron microscopy revealed that the surface of the membrane was smooth, regular and uniform. Fourier transform infrared spectroscopy showed that membrane-forming materials were extremely compatible. The differential scanning calorimeter analysis showed that the composite membrane had the highest thermal enthalpy, reaching 233.940 J/g, with the best thermal stability. When the walnut oil was coated with a composite membrane containing astaxanthin, the oil's peroxide value was reduced by 81.8%, conjugated diene by 44.4% and conjugated triene values by 66.4% compared to the control. Chitosan/soybean protein isolate composite membrane with astaxanthin significantly delayed the process of walnut oil oxidation. [ABSTRACT FROM AUTHOR]

Foods containing tea could be widely utilized due to the addition of good tea ingredients, especially large-leaf yellow tea, which is rich with a good flavor. Applying this change to bread containing tea would improve its product quality. In this research, large-leaf yellow tea bread (LYB), possessing a special flavor, was developed using ultrafine large-leaf yellow tea powder and flour as the main raw materials. The amount of ultrafine large-leaf yellow tea powder added to bread was optimized using texture, sensation, and specific volume as comprehensive evaluation indicators. At the optimal dosage, the free amino acids, volatile flavor compounds, antioxidant activity, and in vitro starch digestibility of LYB were measured. Response surface optimization experimental results showed that the comprehensive score of bread was highest when the added amount of ultrafine large-leaf yellow tea powder was 3%. In particular, compared to blank bread (BB), adding ultrafine large-leaf yellow tea powder into bread could effectively increase its amino acid composition, enhance its volatile flavor compounds, improve the antioxidant capacity, and reduce the digestibility of starch. [ABSTRACT FROM AUTHOR]