Identification of a Single Phosphorylation Site Within Octopus Rhodopsin

Abstract— Light-dependent phosphorylation of rhodopsin (Rho) is a first step in the desensitization of the signaling state of the receptor during vertebrate and invertebrate visual transduction. We found that only ³⁵⁸Ser of the photoac-tivated octopus Rho (oRho*) was phosphorylated by octopus rhodopsin kinase (oRK). Tryptic truncation of the C-terminal PPQGY repeats of oRho that follow the phosphorylation region did not influence spectral or G-protein activation properties of oRho but abolished phos phorylation. Despite significant structural differences between oRK and mammalian RK, these results provide i further evidence of the importance of singly phosphorylated species of Rho* in the generation of arrestin binding sites.     

Quantitative HPTLC Analysis of Palmitoyl Hexapeptide

JPC – Journal of Planar Chromatography – Modern TLC - A sensitive and precise quantitative densitometric HPTLC method has been established for analysis of palmitoyl hexapeptide both as...     

Sensory Rhodopsin I and Sensory Rhodopsin II Form Trimers of Dimers in Complex with their Cognate Transducers

Archaeal photoreceptors consist of sensory rhodopsins in complex with their cognate transducers. After light excitation, a two‐component signaling chain is activated, which is homologous to the chemotactic signaling cascades in enterobacteria. The latter system has been studied in detail. From structural and functional studies, a picture emerges which includes stable signaling complexes, which assemble to receptor arrays displaying hexagonal structural elements. At this higher order structural level, signal amplification and sensory adaptation occur. Here, we describe electron microscopy data, which show that also the archaeal phototaxis receptors sensory rhodopsin I and II in complex with their cognate transducers can form hexagonal lattices even in the presence of a detergent. This result could be confirmed by molecular dynamics calculations, which revealed similar structural elements. Calculations of the global modes of motion displayed one mode, which resembles the “U”‐”V” transition of the NpSRII:NpHtrII complex, which was previously argued to represent a functionally relevant global conformational change accompanying the activation process [Ishchenko et al. (2013) J. Photochem. Photobiol. B 123, 55‐58]. A model of cooperativity at the transmembrane level is discussed.     

Replacement of Two Methylseleno Groups by Two Phenylthio Groups in the Thermal Reaction of 1,2-Bis(methylseleno)-1-phenylethene with Diphenyl Disulfide

Russian Journal of Organic Chemistry -     

Reactions at Only One of Two Equivalent Functional Groups

A common problem encountered by synthetic chemists is to carry out a reaction at just one of two similar functional groups in the substrate molecule. Examples include protection/deprotection of just one hydroxyl group in a diol, addition to only one carbonyl of a diketone, etc. The problem, as depicted below, is to find conditions which maximize formation of the monoproduct (XP) while minimizing the amounts of diproduct (P₂) and starting material (X₂).     

Rhodopsin in a new model bilayer membrane

In search of a planar and uniform model membrane presenting a wide interaction-surface for the study of photobiological processes, we have succeeded in depositing lipid bilayer on a single face of a porous disc. Using a method that combines the Langmuir-Blodgett dipping and the touching procedures, a symmetrical or asymmetrical bilayer membrane has been obtained. The illumination of rhodopsin-containing membranes appears to increase the permeability to K⁺, Na⁺, and Ca²⁺ with a high selectivity for Ca²⁺. The bilayer adsorption on the porous disc is discussed and an attempt is made to explain the failure of the dipping method in our experimental conditions for preparing an artificial membrane. A comparative look at model membranes is also presented.     

Erythemal Ultraviolet Exposure in Two Groups of Outdoor Workers in Valencia, Spain

UVexposure is considered to be one of the most important risk factors in skin cancers, mainly in outdoor occupational activities. Outdoor workers receive regular and significant solar UV erythemal radiation (UVER). To quantify the UVER exposure of certain groups of workers, dosimeters are used to measure the biologically effective UV radiation received in the course of their daily work. Two groups of outdoor workers, composed of gardeners and lifeguards, were measured for UVER exposure using sensitive spore-film filter-type personal dosimeters (Viospor). The study took place in Valencia, Spain, in June and July 2008, and involved one group of four gardeners and another of five beach lifeguards for a period of 4 and 6 days, respectively. The gardeners' mean UV exposure was 4.13 ± 0.60 SED day⁻¹, where 1 SED is defined as effective 100 J m⁻² when weighted with the CIE erythemal response function, whereas the lifeguards received 11.43 ± 2.15 SED day⁻¹. The mean exposure ratio (ER) relative to ambient of gardeners was 0.09 ± 0.01 and for lifeguards was 0.27 ± 0.05. ER is defined as the ratio between the personal dose on a selected anatomical site and the corresponding ambient dose on a horizontal plane during the same exposure period. The lifeguards received the highest UVER exposure, although both groups had measured UVER exposure in excess of occupational guidelines, indicating that protective measures are necessary.     

含噻二唑环的阴离子聚合引发剂在合成双官能团聚氧化乙烯中的应用

以氧化乙烯开环聚合为探针反应,考察了含噻二唑环的新型阴离子聚合引发剂(TDZ-K)的引发活性。反应在非均相中进行,分别用甲醇和甲基丙烯酰氯封端,得含双官能团的氧化乙烯聚合产物,其结构经IR,1H NMR,UV,VPO和GPC表征。加入乙酰丙酮,18-冠-6及PEO作助剂,有助于提高TDZ-K的引发活性。     

Rhodopsin phosphorylation in rats exposed to intense light

The damaging effects of intense light on the rat retina are known to vary depending on the time of day of exposure. The purpose of this study was to determine if rhodopsin phosphorylation patterns, a measure of the activity of the pigment, varied in a similar manner. After 10 min in strong light (1400 lux), all six threonine and serine sites in the rat rhodopsin C-terminus were phosphorylated, with mono- to tetraphosphorylation being substantially more prominent than penta- to hexaphosphorylation. The level and multiplicity of rhodopsin phosphorylations were reduced both with the duration of light exposure and the duration of subsequent darkness. Although showing vast differences in susceptibility to light damage, rats exposed at 5 P.M. or 1 A.M. showed similar rhodopsin phosphorylation levels and patterns. These data indicate that a process controlled by circadian rhythm other than rhodopsin phosphorylation is involved either in damaging or mediating the damage evoked by intense light exposure.     

Transmembrane Signaling Mediated by Water in Bovine Rhodopsin

Abstract— Unhydrated air-dried films of rhodopsin from bovine rod outer segment membranes do not produce its active state, metarhodopsin II. In order to reveal requirements for its formation, we studied changes in H-bonding of water, peptide carbonyl and carboxylic acid in the photochemical reactions by means of difference Fourier transform infrared spectroscopy, under both hydrated and unhydrated conditions. A water molecule near Glull3, which undergoes H-bonding change in bathorhodopsin, remained in the unhydrated film, but with a weaker H-bonding state than in the hydrated film. The other water molecules, which shift in lumirhodopsin and metarhodopsin I as well as in bathorhodopsin of the hydrated film, were not observed in the unhydrated film. Effects of the dehydration were detected in all the C=O stretching vibrations of the peptide backbone and of Asp83 in the formation of bathorhodopsin. The C=O stretching band of Asp83 of lumirhodopsin and metarhodopsin I is intensified in the unhydrated film. We propose that structural changes at the intradiscal site in the interaction between the Schiff base and Glull3 affect water molecules, the peptide backbone, Asp83 and Glul22 in helices B and C through consecutive photochemical processes to metarhodopsin II.     

Identification of Two Transposon-like Elements in Rice Wx Gene

Rice Wx genes have been cloned and sequenced from Oryza saliva subsp. japonica (Wx-R-jp) and subsp. indica (Wx-R-id) and wild rice Oryza saliva L. f. spontanea (Wx-R-sp). Comparison of the nucleotide sequences of these three Wx genes indicates that Wx-R-jp and Wx-R-id genes contain two types of transposon-like elements, designated by RTL-1 and RTL-2. in the region of their two introns and 5' upstream, RTL-1 shares sequence homology with valine tRNA molecules, and contains an internal promoter of RNA polymerase Ⅲ. RTL-2 forms a stem-loop structure. Both RTL-1 and RTL-2 are flanked by direct repetitive sequences. Compared with the elements that have been known transposable, RTL-1 resembles the short interspersed-repeated DNA elements (SINEs) and RTL-2 is similar to the fold-back (FB) element of trahsposon of Drosophila.     

有机官能团性质鉴定设计型实验教学探索

对有机化合物性质实验的实验内容、教学方法、考核方式等全面改革。将传统的单独的验证型实验整合为综合的鉴定设计型实验,学生自主讲解并自行设计未知化合物的鉴定方案,通过多元化的考核方式评定学生的实验成绩,重视对学生实验操作技能、创新能力等综合科学素养的培养,达到了满意的教学效果。     

两种新的多羟基甾醇化合物分离与结构鉴定

采用现代分离手段,从采自中国南海硇洲岛的软珊瑚Chromonephthea sp.中分离纯化得到两种甾醇化合物,经过MS,IR,1H NMR,13C NMR(DEPT),HSQC,HMBC和NOE等光谱技术鉴定它们的结构为:24-甲基胆甾-5-烯-3β,12β,16β,20-四醇(1)和24-乙基胆甾-5-烯-3β,12β,16β,20-四醇(2),这两个化合物均为新化合物.肿瘤活性实验表明两种甾醇化合物显示微弱的细胞毒性.     

Steric Hindrance between Chromophore Substituents as the Driving Force of Rhodopsin Photoisomerization: 10-Methyl-13-Demethyl Retinal Containing Rhodopsin

Abstract— A visual chromophore analogue, 10-methyl-13-demethyl (dm) retinal, was synthesized and reconstituted with bleached bovine rhodopsin to form a visual pigment derivative with absorbance maximum at 505 nm. The investigations with this new compound were stimulated from recent results using 13-dm retinal as a chromophore that revealed a remarkable loss in quantum efficiency (φ of 13-dm retinal-containing rhodopsin: 0.30, Ternieden and Gartner, J. Photochem. Photobiol. B Biol. 33, 83–86, 1996). The quantum efficiency of the new pigment was determined as 0.59 by quantitative bleaching using reconstituted rhodopsin as a reference. The very similar quantum efficiencies of rhodopsin and the new pigment give experimental support for the recently presented hypothesis that a steric hindrance between the substituents at positions 10 and 13 in 11- cis -retinal is elevated during the photoisomerization and thus facilitates the rapid photoisomerization of the visual chromophore (Peteanu et al., Proc. Natl. Acad. Sci. USA 90, 11762–11766, 1993). Such steric hindrance is removed from the molecule by the elimination of the methyl group from position 13 and can be re-established via a rearrangement of the substitution pattern by introducing a methyl group at position 10 of 13-dm retinal.     

对MgO重新水合及两类羟基的研究

采用IR、XRD、TG-DTA等手段对MgO重新水合及其两类羟基进行了研究。发现MgO水解后活性增大,在实验条件下水解仅发生在表面浅层;水合可得到自由、水合两类羟基,600℃灼烧使两类羟基脱除;自由羟基由水合羟基在碱[O^2-]作用下生成;添加Li⁺对表面两类羟基有影响。     

含偶氮苯生色团的聚醚的合成与热致液晶性质

β－氯乙基缩水甘油醚（ＧＣＥ）和ＧＣＥ／羟丁基乙烯基醚（ＨＢＶＥ）分别通过阳离子聚合、光引发共聚合,获得两种聚醚,然后再分别与４－硝基－４’－羟基偶氦苯（ＮＨＡ）反应,制备了两种侧链含偶氦苯生色团的液晶聚合物（ＰＡＥＧ、ＰＡＶ）。用ＦＴＩＲ、＾１Ｈ－ＮＭＲ和ＥＡ对其化学结构及生色团含量进行了表征,以ＰＯＭ,ＤＳＣ、ＴＧＡ和ＷＡＸＤ对聚合物介晶相转变温度、织构、热稳定性及相行为进行了研究。结果表明,     

质谱法鉴定两种化学添加剂中阴离子表面活性剂

本文提出用ＦＡＢ－ＭＳ和ＤＣＩ－ＭＳ法对两种工业化学添加剂中阴离子表面活性剂成份的鉴定方案，方法简便，并对类似未知物的鉴定有参考价值。所得结果为其它方法和应用试验进一步证实。     

Influence of Arrestin on the Photodecay of Bovine Rhodopsin

Continued activation of the photocycle of the dim‐light receptor rhodopsin leads to the accumulation of all‐trans‐retinal in the rod outer segments (ROS). This accumulation can damage the photoreceptor cell. For retinal homeostasis, deactivation processes are initiated in which the release of retinal is delayed. One of these processes involves the binding of arrestin to rhodopsin. Here, the interaction of pre‐activated truncated bovine visual arrestin (Arr^Tr) with rhodopsin in 1,2‐diheptanoyl‐sn‐glycero‐3‐phosphocholine (DHPC) micelles is investigated by solution NMR techniques and flash photolysis spectroscopy. Our results show that formation of the rhodopsin–arrestin complex markedly influences partitioning in the decay kinetics of rhodopsin, which involves the simultaneous formation of a meta II and a meta III state from the meta I state. Binding of Arr^Tr leads to an increase in the population of the meta III state and consequently to an approximately twofold slower release of all‐trans‐retinal from rhodopsin.     

Functional Expression of Gloeobacter Rhodopsin in Synechocystis sp. PCC6803

Proteorhodopsins are light‐driven proton pumps that occur widespread in Nature, where they function predominantly in environments with high incident irradiance. Their maximal absorbance is usually in the blue range, but can be extended into the (far)red range of the electromagnetic spectrum. Because they can be expressed heterologously, they may be exploited in studies aimed at increasing the efficiency of photosynthesis. Here we report further studies toward this goal, by comparing the expression of two different bacterial rhodopsins (Proteorhodopsin and Gloeobacter rhodopsin) in the model cyanobacterium Synechocystis sp. PCC6803. In particular, we investigated the pigments bound by the respective apo‐opsins, and the oligomeric state of the corresponding holo‐rhodopsins, both in Escherichia coli and in the cyanobacterial membranes. We conclude that the two proton‐pumping rhodopsins are predominantly present in an oligomeric state (hexamers for Proteorhodopsin and trimers for Gloeobacter rhodopsin). Furthermore, Gloeobacter rhodopsin is able to bind an antenna carotenoid (in addition to retinal) and has the highest pumping rate at given light intensity. However, its lower expression level will decrease its physiological effectiveness. It remains to be established which of these two bacterial rhodopsins is best in stimulating the growth rate of its cyanobacterial host.