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The NMR studies of the binding of inorganic phosphate, stable form of ATP (dATP), heparin-derived tetrasaccharide to Naja arta cobra cardiotocin A1 (CTX A1) have shown that diverse ligands binding to CTXs might occur at a single protein site with flexible side chain interactions. The results have suggested that the ligand binding site of CTX homologues can be fine-tuned by nonconserved residues near the binding pocket due to their flexible side chain interaction and dimerization ability, even for the rigid CTX molecules tightened by four disulfide bonds.

Natural homologues of cobra cardiotoxins (CTXs) are classified into two structural subclasses of group I and II based on the amino acid sequence and circular dichroism analysis. However, the exact differences in their three-dimensional structures and biological significance remain elusive.

Research has been conducted on cobra cardiotoxin which causes membrane leakage in human erythrocytes. The authors report that this cardiotoxin can cause leakage of vesicle contents in phosphatidylglycerol and phosphatidylserine which contain membrane bilayers.

The predesignable porous structures in metal-organic frameworks (MOFs) render them quite attractive as a host-guest platform to address a variety of important issues at the frontiers of science. In this work, a perfluorophenylene functionalized metalloporphyrinic MOF, namely, PCN-624, has been rationally designed, synthesized, and structurally characterized. PCN-624 is constructed by 12-connected [Ni8(OH)4(H2O)2Pz12] (Pz = pyrazolide) nodes and fluorinated 5,10,15,20-tetrakis(2,3,5,6-tetrafluoro-4-(1H-pyrazol-4-yl)phenyl)-porphyrin (TTFPPP) linker with an ftw-a topological net. Notably, PCN-624 exhibits extinguished robustness under different conditions, including organic solvents, strong acid, and base aqueous solutions. The pore surface of PCN-624 is decorated with pendant perfluorophenylene groups. These moieties fabricate densely fluorinated nanocages resulting in the selective guest capture of the material. More importantly, PCN-624 can be employed as an efficient heterogeneous catalyst for the selective synthesis of fullerene-anthracene bisadduct. Owing to the high chemical robustness of PCN-624, it can be recycled over five times without significant loss of its catalytic activity. All of these results demonstrate that MOFs can serve as a powerful platform with great flexibility for functional design to solve various synthetic problems. [ABSTRACT FROM AUTHOR]

The pre-designable porous structures found in covalent organic frameworks (COFs) render them attractive as a molecular platform for addressing environmental issues such as removal of toxic heavy metal ions from water. However, a rational structural design of COFs in this aspect has not been explored. Here we report the rational design of stable COFs for Hg(II) removal through elaborate structural design and control over skeleton, pore size, and pore walls. The resulting framework is stable under strong acid and base conditions, possesses high surface area, has large mesopores, and contains dense sulfide functional termini on the pore walls. These structural features work together in removing Hg(II) from water and achieve a benchmark system that combines capacity, efficiency, effectivity, applicability, selectivity, and reusability. These results suggest that COFs offer a powerful platform for tailor-made structural design to cope with various types of pollution. [ABSTRACT FROM AUTHOR]

Preparation of two-dimensional layered materials (2DLM) nanosheets is critical for both fundamental studies and applications. Here we present a systematic study to explore the fundamental factors to control the exfoliation of graphite and MoS2 in aqueous N-methylpyrrolidinone (NMP) using water as the cosolvent. Detailed materials characterizations suggested that the cosolvency significantly influences the yield and the stability of exfoliated nanosheets. The dependence of exfoliation on cosolvency was examined by fundamental factors including solid-liquid interfacial parameters, Hansen Solubility Parameter (HSP), and intermolecular-interaction-sensitive physical parameters of the water-NMP mixed solvent system. Fourier transform infrared spectroscopy (FTIR) study revealed that the water-NMP heteroassociated molecular structures, formed with the addition of water to NMP, could play an important role in the liquid exfoliation of layered materials. Our work provides a guide to rational design of a solvent system to improve the yield and stability of the exfoliated materials. [ABSTRACT FROM AUTHOR]

Imine-linked covalent organic frameworks (COFs) were synthesized to bear content-tunable, accessible, and reactive ethynyl groups on the walls of one-dimensional pores. These COFs offer an ideal platform for pore-wall surface engineering aimed at anchoring diverse functional groups ranging from hydrophobic to hydrophilic units and from basic to acidic moieties with controllable loading contents. This approach enables the development of various tailor-made COFs with systematically tuned porosities and functionalities while retaining the crystallinity. We demonstrate that this strategy can be used to efficiently screen for suitable pore structures for use as CO2 adsorbents. The poresurface- engineered walls exhibit an enhanced affinity for CO2, resulting in COFs that can capture and separate CO2 with high performance. [ABSTRACT FROM AUTHOR]

The hydrolytic activity of secretory phospholipase A2(PLA2) is regulated by many factors, including the physical state of substrate aggregates and the chemical nature of phospholipid molecules. In order to achieve strong binding of PLA2on its substrates, many previous works have used anionic lipid dispersion to characterize the orientation and penetration depth of PLA2molecules on membrane surfaces. In this study, we applied monolayer technique with controllable surface area to investigate the PLA2s of Taiwan cobra venom and bee venom on zwitterionic phophatidylcholine monolayers and demonstrated an optimum hydrolytic activity at a surface pressure of 18 and 24 mN/m, respectively. By combining polarized attenuated total reflection Fourier-transform infrared spectroscopy and monolayer-binding experiments, we found that the amount of membrane-bound PLA2decreased markedly as the surface pressure of the monolayer was increased. Interestingly, the insertion area of the PLA2s decreased to near zero as the surface pressure increased to the optimum pressure for hydrolytic activity. On the basis of the measured infrared dichroic ratio, the orientation of the PLA2s bound to zwitterionic membranes was similar to that observed on a negatively charged membrane and was independent of the surface pressure. Our findings suggest that both PLA2s were located on the membrane surface rather than penetrating the membrane bilayer and that the deeply inserted mode is not a favorable condition for the hydrolysis of phospholipids in zwitterionic phospholipid membranes. The results are discussed in terms of the easy access of catalytic water for the PLA2activity and the mobilization of its substrate and product to facilitate the catalytic process. [ABSTRACT FROM AUTHOR]