A General Mechanism of Photoconversion of Green‐to‐Red Fluorescent Proteins Based on Blue and Infrared Light Reduces Phototoxicity in Live‐Cell Single‐Molecule Imaging

Photoconversion of fluorescent proteins by blue and complementary near‐infrared light, termed primed conversion (PC), is a mechanism recently discovered for Dendra2. We demonstrate that controlling the conformation of arginine at residue 66 by threonine at residue 69 of fluorescent proteins from Anthozoan families (Dendra2, mMaple, Eos, mKikGR, pcDronpa protein families) represents a general route to facilitate PC. Mutations of alanine 159 or serine 173, which are known to influence chromophore flexibility and allow for reversible photoswitching, prevent PC. In addition, we report enhanced photoconversion for pcDronpa variants with asparagine 116. We demonstrate live‐cell single‐molecule imaging with reduced phototoxicity using PC and record trajectories of RNA polymerase in Escherichia coli cells.     

含氮芥双-(亚苄基)环烷酮的合成、晶体结构及其体外光动力抗肿瘤活性

为构建光动力治疗与化疗协同抗肿瘤先导化合物,基于药效团拼合原理,设计合成了含氮芥双-(亚苄基)环烷酮化合物3a~3c及对比的双-(亚苄基)环烷酮化合物3d~3f,并经核磁共振波谱仪(NMR)、高分辨质谱HRMS(ESI-MS)、X射线衍射仪(XRD)及傅里叶变换红外光谱仪(FTIR)等技术手段对其进行了结构和性质表征。采用噻唑蓝(MTT)法考察了他们对A549(人肺腺癌细胞)和Hep G2(人源肝癌细胞)的光毒性。结果表明,大部分化合物对两株受试细胞株表现出了一定的光毒性,尤以化合物3a对Hep G2光毒性的半抑制率(IC50)达到2. 0 nmol/m L,值得进一步研究。运用Gaussian09软件,在B3LYP和6-311G+基组水平上对化合物3a和3d进行了量子化学计算并得到其优化构型和分子轨道能量,从前沿轨道能量分析了化合物的结构特征和抗肿瘤活性的构效关系。     

Facile Synthesis of a Phototoxic Monofunctionalized Tetraarylporphyrin as Scaffold for Porphyrin-Quinone Conjugates

A new carboxy-monofunctionalized tertraarylporphyrin has been tested for cytotoxicity toward OV2008 human ovarian cancer cells. This compound acutely inhibits growth of ovarian cancer cells upon exposure to ambient light while suppresses long-term clonogenic survival of cells under both dark and light stimulated conditions. Because of the variable length of the linkage between the anthraquinone and porphyrin moieties, the synthesized monocarboxylated porphyrin presents a versatile scaffold for fine-tuning of the photoelectron transfer in the quinone-porphyrin conjugate. To demonstrate its synthetic value, we converted the carboxy derivative to its amino counterpart.     

Identification of Phototoxic Polycyclic Aromatic Hydrocarbons in Sediments Through Sample Fractionation and QSAR Analysis

Abstract

The toxicity of certain polycyclic aromatic hydrocarbons (PAHs) can be greatly increased by simultaneous exposure of test organisms to ultraviolet (UV) wavelengths present in sunlight. This phenomenon, commonly termed photoinduced toxicity, had been evaluated extensively in laboratory settings where only one chemical of concern was present. However, more recent studies have demonstrated that complex mixtures of PAHs present, for example in sediments, also can cause phototoxicity to a variety of aquatic species when the samples are tested in simulated sunlight. Unfortunately, because these types of samples can contain thousands of substituted and unsubstituted PAHs it is difficult, if not impossible, to use conventional analytical techniques to identify those responsible for photoinduced toxicity. The objective of the present study was to link two powerful ecotoxicology tools, toxicity-based fractionation techniques and QSAR models, to identify phototoxic chemicals in a sediment contaminated with PAHs emanating from an oil refinery. Extensive chromatographic fractionation of pore water from the sediment, in conjunction with toxicity testing, yielded a simplified set of sample fractions containing 12 PAHs that were identified via mass spectroscopy. Evaluation of these compounds using a recently developed QSAR model revealed that, based upon their HOMO-LUMO gap energies, about half were capable of producing photoinduced toxicity. We further evaluated the phototoxic potential of the reduced set of PAHs by determining their propensity to bioaccumulate in test organisms, through calculation of octanol-water partition coefficients for the chemicals. These studies represent a novel linkage of sample fractionation methods with QSAR models for conducting an ecological risk assessment.     

Redox reactions of natural alkaloid lappaconitine

A review on redox reactions of natural alkaloid lappaconitine, a known sodium channel blocker, is presented. The NMR and CIDNP data on the mechanism of phototransformation of lappaconitine, in particular, of its paramagnetic species formed by both the direct photolysis and photoinitiated interaction with electron donors and acceptors, are analyzed. Special attention is given to the interaction of lappaconitine with amino acids, which are present in the active site of the sodium channel. Hypotheses about a relationship between this process and the mechanism of therapeutic activity of lappaconitine are discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 608–619, April, 2007.     

Synthesis and antimycotic activity of new unsymmetrical substituted zinc phthalocyanines

The synthesis of new unsymmetrical substituted zinc phthalocyanines derivatives has been described; moreover the photodynamic activity of some compounds tested against Candida albicans has been reported.     

Crystal structure of the potent bisquinoline antimalarial agent (±)-trans-N 1,N 2-bis(7-chloroquinolin-4-yl) cyclohexane-1,2-diamine dimethanesulfonate salt hydrate in relation to its biological properties

The neighboring 4-aminoquinoline substituents of the bisquinoline (±)-trans-N ¹,N ²-bis(7-chloroquinolin-4-yl)cyclohexane-1,2-diamine dimethanesulfonate salt crystallized in the diequatorial position which is in agreement with quantum chemical calculations. The bisquinoline salt crystallized in the monoclinic C2/c space group with a = 19.328(4) Å, b = 15.618(3) Å, c = 20.382(4) Å, = 98.84(3)°. The two quinoline nitrogen atoms are protonated by the salt as predicted by calculated electrostatic surface potentials. The –5 kcal/mol isopotential surface of the bisquinoline resembles that of chloroquine, which may explain the potent inhibition of hematin polymerization by both the bisquinoline and chloroquine. The smaller HOMO/LUMO gap of the bisquinoline is consistent with its phototoxicity. The overall conformation, the ability of all nitrogen atoms to participate in hydrogen bonding, and the electrostatic interaction of the quinoline rings in the crystal packing may all aid in the determination of the binding pharmacophore of the bisquinoline.     

Porphyrin‐functionalized amphiphilic diblock copolypeptides for photodynamic therapy

A series of amphiphilic diblock copolypeptides (ADCs), 5‐(4‐aminophenyl)‐10,15,20‐triphenyl‐porphyrin (APP) conjugated poly(L ‐leucine)‐block‐polylysine (APP‐L_nK_m) with different molar ratios of L ‐leucine unit and lysine unit were designed and synthesized. The optimized composition of the polypeptide was determined to be APP‐L₁₀₉K₁₈₆, which has high fluorescence quantum yield and could self‐assemble into micelles in an aqueous medium with mean particle size <30 nm. The in vitro study indicates that APP‐L₁₀₉K₁₈₆ shows no significant dark cytotoxicity when the concentration is below 200 mg L^?1 for HepG2 and HeLa cells. In contrast, the polymer exhibits apparent phototoxicity with low IC₅₀ values toward HepG2 and HeLa cells, implying that the potential high photodynamic therapy efficacy of the polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010