Controlling the thermally-driven crystallization of DNA-coated nanoparticles with formamide.

DNA-coated nanoparticles, also known as programmable atom equivalents (PAEs), facilitate the construction of materials with nanoscopic precision. Thermal annealing plays a pivotal role by controlling DNA hybridization kinetics and thermodynamics, which ensures the formation of intended structures. While various design handles such as particle size, DNA design, and salt concentration influence the stability of the DNA duplexes linking PAEs in a lattice, their influence on the system's melting temperature (Tm) often follows complicated trends that make rational tuning of self-assembly challenging. In this work, the denaturant formamide is used to precisely tune the thermal response of PAEs. Our results reveal a clear and predictable trend in the PAEs' response to formamide, enabling rational control over the Tm of a diverse set of PAE systems. Unlike adjustments made through alterations to PAE design or solution parameters such as ionic strength, formamide achieves its temperature shift without impacting the kinetics of assembly. As a result, PAEs can be rapidly crystallized at ambient temperatures, producing superlattices with similar quality to PAE crystals assembled through standard protocols that use higher temperatures. This study therefore positions formamide as a useful tool for enhancing the synthesis of complex nanostructures under mild conditions.

Discovery and Biosynthesis of Cihunamides, Macrocyclic Antibacterial RiPPs with a Unique C-N Linkage Formed by CYP450 Catalysis.

Cihunamides A-D (1-4), novel antibacterial RiPPs, were isolated from volcanic-island-derived Streptomyces sp. The structures of 1-4 were elucidated by 1 H, 13 C, and 15 N NMR, MS, and chemical derivatization; they contain a tetrapeptide core composed of WNIW, cyclized by a unique C-N linkage between two Trp units. Genome mining of the producer strain revealed two biosynthetic genes encoding a cytochrome P450 enzyme and a precursor peptide. Heterologous co-expression of the core genes demonstrated the biosynthesis of cihunamides through P450-mediated oxidative Trp-Trp cross-linking. Further bioinformatic analysis uncovered 252 homologous gene clusters, including that of tryptorubins, which possess a distinct Trp-Trp linkage. Cihunamides do not display the non-canonical atropisomerism shown in tryptorubins, which are the founding members of the "atropitide" family. Therefore, we propose to use a new RiPP family name, "bitryptides", for cihunamides, tryptorubins, and their congeners, wherein the Trp-Trp linkages define the structural class rather than non-canonical atropisomerism.

Complete atrioventricular nodal block after propofol administration in an elderly patient undergoing total knee replacement arthroplasty -A case report-.

Complete atrioventricular (AV) block is defined as a dissociation of atrial and ventricular activities. Complete AV block that occurs during the perioperative period is difficult to reverse and usually requires implantation of a pacemaker. Propofol does not affect a normal AV conduction system but may act as a trigger for AV block. It can also potentiate vagal stimulation factors and reduce sympathetic activity. We report a case of complete AV block that may have been related to administration of propofol.