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AIM: To investigate the effects of baffle and intraocular pressure (IOP) on the aerosols generated in the noncontact tonometer (NCT) measurement and provide recommendations for the standardized use of the NCT during coronavirus disease 2019 (COVID-19). METHODS: This clinical trial included 252 subjects (312 eyes) in The Eye Hospital, Wenzhou Medical University from March 7, 2020, to March 28, 2020. Sixty subjects (120 eyes) with normal IOP were divided into two groups. One group used an NCT without a baffle, another group used an NCT with a baffle. Another 192 subjects (192 eyes) were divided into four groups: Group A(1) (without a baffle+normal IOP), Group A(2) (without a baffle+high IOP), Group B(1) (with a baffle+normal IOP) and Group B(2) (with a baffle+high IOP). Particulate matter (PM) 2.5 and PM10 generated by all subjects were quantified during the NCT measurement. The IOP values were recorded simultaneously. Effects of baffle and IOP on aerosols generated during the NCT measurement were analyzed. RESULTS: In the normal eye group with a baffle, the aerosol density decreased in a wave-like shape near the NCT with the increase in the number of people measured for IOP, demonstrating no cumulative effect. However, in the normal eye group without a baffle, there was a cumulative effect. PM2.5 and PM10 in Group A(2) were higher than Group A(1) (both P

All known riboswitches use their aptamer to senese one metabolite signal and their expression platform to regulate gene expression. Here, we characterize a SAM-I riboswitch (SAM-IXcc) from the Xanthomonas campestris that regulates methionine synthesis via the met operon. In vitro and in vivo experiments show that SAM-IXcc controls the met operon primarily at the translational level in response to cellular S-adenosylmethionine (SAM) levels. Biochemical and genetic data demonstrate that SAM-IXcc expression platform not only can repress gene expression in response to SAM binding to SAM-IXcc aptamer but also can sense and bind uncharged initiator Met tRNA, resulting in the sequestering of the anti-Shine-Dalgarno (SD) sequence and freeing the SD for translation initiation. These findings identify a SAM-I riboswitch with a dual functioning expression platform that regulates methionine synthesis through a previously unrecognized mechanism and discover a natural tRNA-sensing RNA element. This SAM-I riboswitch appears to be highly conserved in Xanthomonas species., Riboswitches consist of an aptamer domain and expression platform, which senses a signal and regulates gene expression, respectively. Here the authors show that the expression platform of a SAM-I riboswitch from the Gram-negative bacteria can sense and bind uncharged an initiator Met tRNA to control the met operon.

We report the synthesis of zwitterionic homopolypeptides and block copolypeptides bearing carboxybetaine and sulfobetaine (CB and SB) via combining γ-propargyl-L-glutamate NCA polymerization with efficient Huisgen's click reaction. The zwitterionic homopolypeptides adopted versatile chain conformations upon varying the solution pH, depending on the chain length and functional group. The zwitterionic homopolypeptides with a degree of polymerization (DP) of 60 adopted stable α-helical conformation due to their elongated side-chain, whereas the short ones (DP = 20) adopted different conformations at varying solution pH. Their interactions with proteins depend on the chain conformation and zwitterionic group. The short one bearing SB exhibited very low interactions with lysozyme and myoglobin due to its coil and zwitterionic nature. A preliminary study showed that the zwitterionic block copolypeptides self-assemble to form vesicles with tunable molecular packing and solution behavior. These biodegradable/biocompatible, zwitterionic polypeptides may be promising materials in many applications such as non-fouling coatings and drug delivery.