First preparation of biotinylated gradient polyethylene surface to bind photoactive caged streptavidin

A gradient polyethylene (PE) surface was created through corona treatment, in which the corona power increased along the 5 cm length of the PE. The gradient surface was treated with polyethyleneimine and then biotin. Fluorescein-conjugated streptavidin (SAV) caged within 5-carboxymethoxy-2-nitrobenzyl (CMNB) adsorbed onto the biotinylated gradient PE surface following molecular recognition principles. Photoirradiation decomposed the CMNB cage and allowed the fluorescein-conjugated SAV to fluoresce, the intensity of which increased gradually along the PE surface.     

Selective binding of steroids by 2,2'-biquinoline-4,4'-dicarboxamide-bridged bis(beta-cyclodextrin): fluorescence enhancement by guest inclusion

A novel bis(beta-cyclodextrin) was synthesized, and its binding behavior with steroids was investigated to demonstrate that the cooperative co-inclusion of guest and tether by two cyclodextrin moieties is operative to afford the highest molecular selectivity of up to 3.6 for deoxycholate over taurocholate.     

A SAPO-11 Silicoaluminophosphate Molecular Sieve with Stable Crystal Structure

A SAPO-11 silicoaluminophosphate molecular sieve with stable crystal structure was synthesized for the first time. After removing template by calcination, its crystal space group still retains Icm2 which the as-synthesized has. The catalyst deriving from the present SAPO-I 1 materials shows higher isomerization selectivity and higher paraffin hydroisomerization yield than those reported elsewhere.     

The kinetics of cation exchange reaction of europium propylenediaminetetraacetate with ytterbium ion

The kinetics of cation exchange reaction of Eu(III) propylenediaminetetraacetate with Yb(III) has been studied in an aqueous solution by the polarographic procedure. The measurements were made at 25°C and at an ionic strength of 0.5 M KCl. The dissociation of the europium complex has been found to be catalyzed by hydrogen ions. The influences of the inductive effect and the steric hindrance of a C-methyl group on the ethylene of PDTA are discussed by comparing it to analogous EDTA and CyDTA system.     

新冠病毒刺突蛋白及其受体的结构与相互作用

Biochemistry is a branch subject of chemistry, which is the study of chemical structures and processes associated with living organisms. COVID-19 pandemic is a problem for human beings. From the perspective of biochemistry, this paper demonstrates the chemical structure and interactions of SARS-CoV-2's spike protein and its receptor (human angiotensin converting enzyme 2), and summarizes the related research progresses. The authors hope to provide insights for the development of COVID-19 vaccine.     

Four New Podocarpane‐Type Trinorditerpenes from Aleurites moluccana

Four new podocarpane‐type trinorditerpenenes, (5β,10α)‐12,13‐dihydroxypodocarpa‐8,11,13‐trien‐3‐one ( 1 ), (5β,10α)‐12‐hydroxy‐13‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 2 ), (5β,10α)‐13‐hydroxy‐12‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 3 ), and (3α,5β,10α)‐13‐methoxypodocarpa‐8,11,13‐triene‐3,12‐diol ( 4 ), together with four known diterpenes, 12‐hydroxy‐13‐methylpodocarpa‐8,11,13‐trien‐3‐one ( 5 ), spruceanol ( 6 ), ent‐3α‐hydroxypimara‐8(14),15‐dien‐12‐one ( 7 ), and ent‐3β,14α‐hydroxypimara‐7,9(11),15‐triene‐12‐one ( 8 ), were isolated from the twigs and leaves of Aleurites moluccana. Their structures were elucidated by means of comprehensive spectroscopic analyses, including NMR and MS. Except 8 , all compounds were evaluated for their cytotoxicity; compound 4 exhibited moderate inhibitory activity against Raji cells with an IC₅₀ value of 4.24 μg/ml.     

Tocopherols and Triterpenoids from Sida acuta

A new tocopherol derivative, 7_a‐methoxy‐α‐tocopherol ( 1 ), and a new taraxastane triterpene, taraxast‐1,20(30)‐dien‐3‐one ( 5 ), together with four known compounds, β‐tocopherol ( 2 ), α‐tocopherol ( 3 ), α‐tocospiro B ( 4 ) and taraxasterone ( 6 ) were isolated from the whole plant of Sida acuta. Their structures were elucidated by spectral analysis including MS, 1D and 2D‐NMR spectroscopy. Among those compounds, compounds 1 , 2 , and 3 showed significant antioxidant effect (EC₅₀ = 86.9, 68.2, and 70.9 μM, respectively) in the DPPH radicals scavenging activity assay.     

Poly（meta-phenylene） Derivative with Rigid Twisted Biphenyl Units in Backbone： Synthesis, Structural Characterization, Photophysical Properties and Electroluminescence

A soluble poly(meta-phenylene)derivative with rigid twisted biphenyl unit was synthesized by the Yamamoto coupling reaction.The polymer is soluble in common organic solvents,and the number-average molecular weight is about 6500.The UV-Vis and quantum chemical calculation indicate that the different conformation segments named "conformers" exist in the polymer backbones;it was also further confirmed by the single crystal X-ray diffraction study of the dimeric model compound.The π-π transition of biphenyl segments of twisted and planar conformations made the polymer exhibit a strong absorption around 256 nm and a weak absorption at about 300 nm.Furthermore,the polymer exhibits a strong UV photoluminescence at 372 nm when the excitation wavelengths are longer than 300 nm.The ultraviolet-emitting electroluminescence(EL)device with the single layer structure shows EL λmax of the derivative at 370 nm.     

catena‐Poly[[tetra­aqua­manganese(II)]‐μ‐4‐(carboxyl­ato­methyl­sulfanyl)­phenoxy­acetato]

The title compound, [Mn(C₁₀H₈O₅S)(H₂O)₄]_n, a one‐dimensional manganese(II) complex comprising helical chains bridged by 4‐(carboxylatomethylsulfanyl)phenoxyacetate ligands has been characterized by single‐crystal X‐ray diffraction analysis. Hydrogen‐bonding inter­actions between adjacent chains extend the complex into a three‐dimensional supra­molecular architecture.     

A Novel Fluorescent Aminoacid Designed for Fluorometric Detection of Cu （Ⅱ）

A fluorescent aminoacid was designed for selective and sensitive detection of Cu(II) in aqueous solution. The designing of this Cu(II) fluorescent chemosensing molecule, N ± (1‐naphthyl). aminoacetic acid (NAA), was based on the binding of Cu(II) to aminoacetic acid and the novel charge transfer photophysics of 1‐aminonaphthalenes. The fluorescence of NAA was found quenched by Cu (II) and several other metal ions of similar electronic structure such as Co(II), Ni(II) and Zn(II). The quenching was shown to occur via electron transfer within the metal‐NAA complex, which required an optimal combination of high binding affinity and favorable redox properties of the components in the metal‐NAA complex and hence afforded selective fluorometric detection of Cu(II). The calibration graph obeyed Stern‐Volmer theory and was shown for Cu(II) over the range of 0–2.75 ± 10–⁴ mol/L. The quenching constant of Cu(II) was measured as 8.0 ± 10³ mol/L that was two orders of magnitude higher than those of Co(II), Ni(II) and Zn(II). The 3SD limit of detection for Cu(II) was 8.00 ± 10^?6 mol/L with a coefficient of variation of 1.65%. Linear range for quantitative detection of Cu(II) was 2.67 ± 10^?5‐2.75 ± 10^?4 mol/L. The method was applied to synthetic sample measurements which gave recoveries of 105%‐112%.