Advances in understanding the molecular basis of the first steps in color vision

Serving as one of our primary environmental inputs, vision is the most sophisticated sensory system in humans. Here, we present recent findings derived from energetics, genetics and physiology that provide a more advanced understanding of color perception in mammals. Energetics of cis–trans isomerization of 11-cis-retinal accounts for color perception in the narrow region of the electromagnetic spectrum and how human eyes can absorb light in the near infrared (IR) range. Structural homology models of visual pigments reveal complex interactions of the protein moieties with the light sensitive chromophore 11-cis-retinal and that certain color blinding mutations impair secondary structural elements of these G protein-coupled receptors (GPCRs). Finally, we identify unsolved critical aspects of color tuning that require future investigation.     

Climatic droplet keratopathy: an old disease in new clothes

Climatic droplet keratopathy (CDK) is an acquired and potentially handicapping cornea degenerative disease that is highly prevalent in certain rural communities around the world. It predominantly affects males over their forties. It has many other names such as Bietti's band‐shaped nodular dystrophy, Labrador keratopathy, spheroidal degeneration, chronic actinic keratopathy, oil droplet degeneration, elastoid degeneration and keratinoid corneal degeneration. CDK is characterized by the haziness and opalescence of the cornea's most anterior layers which go through three stages with increasing severity. Globular deposits of different sizes may be histopathologically observed under the corneal epithelium by means of light and electron microscopy. The coalescence and increased volume of these spherules may cause the disruption of Bowman's membrane and the elevation and thinning of the corneal epithelium. The exact aetiology and pathogenesis of CDK are unknown, but they are possibly multifactorial. The only treatment in CDK advanced cases is a corneal transplantation, which in different impoverished regions of the world is not an available option. Many years ago, the clinical and histological aspects of this disease were described in several articles. This review highlights new scientific evidence of the expanding knowledge on CDK's pathogenesis which will open the prospect for new therapeutic interventions.     

Calendering as a direct shaping tool for the continuous production of fixed-dose combination products via co-extrusion

In this study calendering is used as a downstream technique to shape monolithic co-extruded fixed-dose combination products in a continuous way. Co-extrudates with a metoprolol tartrate-loaded sustained-release core and a hydrochlorothiazide-loaded immediate-release coat were produced and immediately shaped into a monolithic drug delivery system via calendering, using chilled rolls with tablet-shaped cavities. In vitro metoprolol tartrate release from the ethylcellulose core of the calendered tablets was prolonged in comparison with the sustained release of a multiparticulate dosage form, prepared manually by cutting co-extrudates into mini-matrices. Analysis of the dosage forms using X-ray micro-computed tomography only detected small differences between the pore structure of the core of the calendered tablet and the mini-matrices. Diffusion path length was shown to be the main mechanism behind the release kinetics. Terahertz pulsed imaging visualized that adhesion between the core and coat of the calendered tablet was not complete and a gradient in coat thickness (varying from 200 to 600 μm) was observed. Modulated differential scanning calorimetry and X-ray diffraction indicated that the solid-state properties of both drugs were not affected by the calendering procedure.     

分光光度法测定红花软胶囊中总黄酮的含量

目的：建立红花软胶囊中总黄酮含量的检测方法。方法：采用UV法,在波长360nm处测定红花软胶囊中总黄酮的含量。结果：用芦丁作对照,在4.657～23.285μg/mL范围内线性关系良好,r=1.0000,平均回收率为97.10%（RSD=1.1%,n=9）。结论：该方法准确、灵敏、重现性好,可用于红花软胶囊中总黄酮含量的测定。     

紫外分光光度法测定阿替洛尔缓释微囊含量

目的：建立以紫外分光光度法测定阿替洛尔缓释微囊含量的方法。方法：将阿替洛尔缓释微囊研磨破碎,转移至容量瓶中,稀释后,在224nm处进行含量测定。结果：阿替洛尔在224nm处有最大吸收,辅料对测定无干扰。标准曲线方程：A=0.0355C+0.0014,线性范围为2.5～20.0μg·ml-1。回收率98.81%～99.36%,精密度和稳定性RSD均在2%以内,符合《中国药典》的要求。     

大孔吸附树脂分离纯化淫羊藿EF5黄酮

目的：采用HPLC法和UV法监测AB-8大孔吸附树脂分离纯化以淫羊藿苷、朝藿定A、朝藿定B、朝藿定C和宝藿苷I这五种黄酮为主要成分的淫羊藿EF5黄酮并筛选出最佳分离纯化工艺参数。方法：采用UV法,以淫羊藿总黄酮洗脱率为指标,考察树脂对淫羊藿总黄酮的吸附容量、解吸附率、吸附动力学,以确定树脂分离纯化淫羊藿EF5黄酮的最佳吸附性能;采用HPLC法,以淫羊藿EF5黄酮中五种黄酮单体的洗脱率为指标,考察洗脱液浓度和洗脱液用量等参数,确定淫羊藿EF5黄酮的最佳洗脱参数。结果：AB-8大孔吸附树脂对淫羊藿总黄酮的吸附容量以湿树脂计为（58.37±2.36）mg·g-1,解吸附率为（86.77±2.32）%,最佳吸附时间为180min,最佳洗脱液为60%乙醇,最佳洗脱液用量为5BV,纯化后真空干燥所得棕褐色淫羊藿EF5黄酮粉末中朝藿定A、朝藿定B、朝藿定C、淫羊藿苷和宝藿苷I的含量分别为3.51%、4.87%、1.22%、33.05%、1.36%,淫羊藿EF5黄酮纯度为44%。结论：AB-8大孔吸附树脂分离纯化得到的淫羊藿EF5黄酮的纯度较高,适合工业生产。     

Nucleotide excision repair by dual incisions in plants

Plants use light for photosynthesis and for various signaling purposes. The UV wavelengths in sunlight also introduce DNA damage in the form of cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts [(6-4)PPs] that must be repaired for the survival of the plant. Genome sequencing has revealed the presence of genes for both CPD and (6-4)PP photolyases, as well as genes for nucleotide excision repair in plants, such as Arabidopsis and rice. Plant photolyases have been purified, characterized, and have been shown to play an important role in plant survival. In contrast, even though nucleotide excision repair gene homologs have been found in plants, the mechanism of nucleotide excision repair has not been investigated. Here we used the in vivo excision repair assay developed in our laboratory to demonstrate that Arabidopsis removes CPDs and (6-4)PPs by a dual-incision mechanism that is essentially identical to the mechanism of dual incisions in humans and other eukaryotes, in which oligonucleotides with a mean length of 26–27 nucleotides are removed by incising ∼20 phosphodiester bonds 5′ and 5 phosphodiester bonds 3′ to the photoproduct.Plants and other organisms that depend on photosynthesis are, by necessity, exposed to more sunlight than other organisms that are chemotrophs or heterotrophs. Hence, plants are expected to receive more exposure to UV wavelengths of light than other organisms. The genotoxic effects of UV are somewhat mitigated by the reflection of UV by the waxy leaf surface and absorbance of UV by the intracellular pigments that are present at high concentration in plant cells, including carotenoids and flavonoids. Nevertheless, plants still receive considerable amounts of DNA-damaging UV radiation and therefore must have the means to cope with the damage to ensure their survival. Indeed, DNA sequencing has revealed that plant genomes contain genes that are homologous to the genes of all major DNA repair pathways, including photoreactivation, nucleotide excision repair, base excision repair, and recombination/double-strand break repair (1–6).However, biochemical studies of these DNA repair mechanisms have been limited. Of significance, Arabidopsis photolyases have been expressed in heterologous systems, purified, and characterized (7–9). Similarly, some of the enzymes of the base excision repair and recombination/double-strand break repair systems have been studied. In contrast, there have been no mechanistic studies on plant nucleotide excision repair, although it is known that plants can remove cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts [(6-4)PPs] in a photolyase-independent manner (6, 10, 11), presumably by nucleotide excision repair. Here, we have used an Arabidopsis cell line and the in vivo excision assay recently developed in our laboratory (12–14) to demonstrate that Arabidopsis removes these photoproducts by dual incisions in a manner that is virtually identical to human nucleotide excision repair.     

Bioinspired Photo‐Core‐Crosslinked and Noncovalently Connected Micelles From Functionalized Polystyrene and Poly(ethylene oxide) Homopolymers

In this paper, we report a simple and effective method for the preparation of stable core‐crosslinked micelles after the self‐assembly of thymine‐functionalized polystyrene (PVBT) and adenine‐terminated poly(ethylene oxide) (PEO‐A) homopolymers, and subsequent bioinspired photo‐crosslinking of the thymine units in PVBT. We obtained “graft‐like” copolymers from the interactions of PEO‐A with the PVBT chains through complementary multiple hydrogen bonding in a common solvent (dimethylformamide) after the addition of selective solvents (H₂O and MeCN for PVBT and PEO‐A, respectively). Stable micelles featuring PVBT as the core and PEO‐A as the shell were formed via selective solvent pairs; they were clearly visualized using transmission electronic microscopy and staining techniques. The shapes and sizes of the core/shell micelle structures did not change after exposure to UV light, revealing the enhanced dimensional stability of these photo‐core‐crosslinked micelles.     

Parameter Study on the Preparation of UV Depth‐Cured Chemically Resistant Polysulfone‐Based Membranes

Polysulfone‐based membranes with excellent chemical resistance and a wet thickness up to 200 μm are obtained via UV curing of unmodified polymers after careful tuning of the photoinitiating system and the crosslinker structure. Combinations of photoinitiator and crosslinker are studied in depth, followed by a characterization of the formed macromolecular structure. The performance of the resulting membranes is then evaluated through long‐term immersion in solvents. Classical depth‐curing acyl phosphine oxide‐based photoinitiators in combination with a pentaacrylate crosslinker are found to be the optimal system.

     

Identification of the designer steroid Androsta‐3,5‐diene‐7,17‐dione in a dietary supplement

A liquid chromatography‐mass spectrometry (LC–MS) screen for known anabolic‐androgenic steroids in a dietary supplement product marketed for “performance enhancement” detected an unknown compound having steroid‐like spectral characteristics. The compound was isolated using high performance liquid chromatography with ultraviolet detection (HPLC–UV) coupled with an analytical scale fraction collector. After the compound was isolated, it was then characterized using gas chromatography with simultaneous Fourier Transform infrared detection and mass spectrometry (GC–FT–IR–MS), liquid chromatography–high resolution accurate mass–mass spectrometry (LC–HRAM–MS) and nuclear magnetic resonance (NMR). The steroid had an accurate mass of m/z 285.1847 (error?0.57 ppm) for the protonated species [M + H]⁺, corresponding to a molecular formula of C₁₉H₂₄O₂. Based on the GC–FT–IR–MS data, NMR data, and accurate mass, the compound was identified as androsta‐3,5‐diene‐7,17‐dione. Although this is not the first reported identification of this designer steroid in a dietary supplement, the data provided adds information for identification of this compound not previously reported. This compound was subsequently detected in another dietary supplement product, which contained three additional active ingredients.