Tetrachromacy, oil droplets and bird plumage colours

There is a growing body of data on avian eyes, including measurements of visual pigment and oil droplet spectral absorption, and of receptor densities and their distributions across the retina. These data are sufficient to predict psychophysical colour discrimination thresholds for light-adapted eyes, and hence provide a basis for relating eye design to visual needs. We examine the advantages of coloured oil droplets, UV vision and tetrachromacy for discriminating a diverse set of avian plumage spectra under natural illumination. Discriminability is enhanced both by tetrachromacy and coloured oil droplets. Oil droplets may also improve colour constancy. Comparison of the performance of a pigeon's eye, where the shortest wavelength receptor peak is at 410 nm, with that of the passerine Leiothrix, where the ultraviolet-sensitive peak is at 365 nm, generally shows a small advantage to the latter, but this advantage depends critically on the noise level in the sensitivity mechanism and on the set of spectra being viewed. Accepted: 3 July 1998     

Production of toluene cis-diol by immobilized pseudomonas putida UV4 cells in barium alginate beads

In the present study, we have investigated the biotransformation of toluene to its cis-dihydrodiol (cis-diol) with immobilized Pseudomonas putida UV4 cells using different conditions of immobilization with a view to improving its production. The choice of alginate and its concentration for the immobilization of the cells were found to be the most important factors affecting the production of toluene cis-diol. The concentration of minerals and oxygen in the reaction medium and the methodology of substrate addition were investigated and the optimal conditions were defined. Once the optimal conditions for biotransformations and entrapment were determined, a packed-bed and fluidized-bed reactor were evaluated for the biotransformation process. The results using air as the gas supply showed an increase in the total production from 0.15 mol cis-diol · g⁻¹ dry cell weight (dcw) in the packed-bed reactor to 0.28 mol cis-diol · g⁻¹ dcw in the fluidized-bed reactor. When pure oxygen was used in place of air in the fluidized-bed reactor, a dramatic increase in total production up to a maximum of 6.1 mol cis-diol · g⁻¹ dcw using a medium flow rate of 100 ml min⁻¹ was achieved. Under optimal conditions, a maximum rate of production of 86.9 mmol cis-diol g⁻¹ dcw h⁻¹ was achieved for 48 h. This was seven times higher than the rate previously reported in the literature and for a much longer period of time; consequently, the overall production observed was more than 75 times higher than the values reported in the literature.     

马铃薯栽培种和野生种叶肉原生质体紫外线辐射效应

4个马铃薯栽培种和4个野生种叶肉原生质体黑暗中进行紫外线辐射处理。观察了不同剂量紫外线照射对原生质体分裂生长的影响。S.demissum,S.tuberosum,S.bulbocastum,S.phureja和S.brevidens最低失活剂量分别为8min,5.5min,4.0min,2.0min和15min。３种紫外线照射方式中,“15w,60cm”照射方式失活效果最好。刚分离的原生质体对紫外线最敏感,随着原生质体培养进程,其紫外线抗性逐渐增强。基因型、倍性水平、原生质体体积对原生质体紫外线失活剂量有影响。     

牛红细胞超氧化物歧化酶活性中心的紫外光谱研究

应用差示分光光度法研究了牛红细胞Ｃｕ２Ｚｎ２ＳＯＤ的紫外光谱,归属和讨论了酶活性中心金属离子与配体间全部电荷转移谱带,给出了相应的配体轨道光学电负性,特别研究了涉及Ｚｎ２＋的电荷转移谱带．     

Further characterization of two different,reversible aldehyde oxidoreductases from Clostridium formicoaceticum,one containing tungsten and the other molybdenum

The tungsten- and the molybdenum-containing aldehyde oxidoreductases from Clostridium formicoaceticum show, for aldehydes, K _m values<30 M and K _i values of millimolar concentrations. The tungsten-containing aldehyde oxidoreductase is inactivated to 50% by 3 mM KCN within 1 min, by 1 mM ferricyanide within 5 min, and by 0.05 mM chloralhydrate within 30 s. The molybdenum-containing AOR shows 50% inactivation within 1 min only with 70 mM KCN. The tungsten-containing enzyme is very sensitive to oxygen, especially in the reduced state, whereas the molybdenum-containing enzyme exhibits only moderate oxygen sensitivity without being markedly influenced by the redox state of the enzyme. The tungsten in the aldehyde oxidoreductase is bound to a pterin cofactor (Wco) of the mononucleotide form that is known for molybdopterin cofactor (Moco). The nature of the molybdenum cofactor in the molybdenum-containing aldehyde oxidoreductase is still unclear. The UV/VIS spectrum of the tungsten-containing aldehyde oxidoreductase shows a broad absorption in the range of 400 nm with a millimolar absorption coefficient of 18.1 (reduced form) and 24.8 (dehydrogenated form) at 396 nm. The epr spectrum exhibits two different W(V) signals with the following g values for signal A: 2.035, 1.959, 1.899 and signal B: 2.028, 2.017, 2.002. Dithionite-reduced enzyme shows signals of 4Fe–4S or 2Fe–2S clusters. Initial rate studies with different substrates for the carboxylate reduction led to a Bi Uni Uni Bi mechanism.Abbreviations AOR aldehyde oxidoreductase - NH ₂ CO-MV 1,1-carbamoylmethylviologen - MV methylviologen - TMV 1,1,2,2-tetramethylviologen     

辣椒果实中类胡萝卜素的组成

本文采用薄层层析法分析了成熟辣椒果实中类胡萝卜素的组成及主要类胡萝卜素的相对含量。用溶剂油从红辣椒干果皮中抽提类胡萝卜素,经除辣味处理后得到类胡萝卜素混合物,并对其进行皂化。以硅胶Ｇ为固定相,正己烷／乙酸乙脂／丙酮／甲醇（８０／１０／５／５）为展开剂,对类胡萝卜素皂化后混合物进行层析,依此法可分离出清晰的１３个有色斑点。对这些斑点作紫外可见光谱分析．由最大吸收峰和极性判断各斑点的成分,并由吸光植计算其相对含量。     

PHOTOSYNTHETIC INSENSITIVITY OF THE TERRESTRIAL CYANOBACTERIUM NOSTOC FLAGELLIFORME TO SOLAR UV RADIATION WHILE REHYDRATED OR DESICCATED1

Photosynthetic performance of the terrestrial cyanobacterium Nostoc flagelliforme (M. J. Berkeley et M. A. Curtis) Bornet et Flahault during rehydration and desiccation has been previously characterized, but little is known about the effects of solar UV radiation (280–400 nm) on this species. We investigated the photochemical activity during rehydration and subsequent desiccation while exposing the filamentous colonies to different solar radiation treatments. Photochemical activity could be reactivated by rehydration under full‐spectrum solar radiation, the species being insensitive to both ultraviolet‐A radiation (UVAR; 315–400 nm) and ultraviolet‐B radiation (UVBR). When the rehydrated colonies were exposed for desiccation, the effective PSII photochemical yield was inhibited by visible radiation (PAR) at the initial stage of water loss, then increased with further decrease in water content, and reached its highest value at the water content of 10%–30%. However, no significant difference was observed among the radiation treatments except for the moment when they were desiccated to critical water content of about 2%–3%. At such a critical water content, significant reduction by UVBR of the effective quantum yield was observed in the colonies that were previously rehydrated under indoor light [without ultraviolet radiation (UVR)], but not in those reactivated under scattered or direct solar radiation (with UVR), indicating that preexposure to UVR during rehydration led to higher resistance to UVR during desiccation. The photosynthetic CO₂ uptake by the desiccated colonies was enhanced by elevation of CO₂ but was not affected by both UVAR and UVBR. It increased with enhanced desiccation to reach the maximal values at water content of 40%–50%. The UV‐absorbing compounds and the colony sheath were suggested to play an important role in screening harmful UVR.     

The problem of political blackness: lessons from the Black Supplementary School Movement

The Black Supplementary School Movement has a fifty-year tradition of resisting racism in Britain. Central to the movement is a construction of African Diasporic Blackness that is marginalized in British scholarship. ‘Political blackness’, based on the unity ethnic minority groups, is an important frame of reference in Britain. This article will examine the limitations of ‘political blackness’ in relation to research carried out in the Black Supplementary School Movement that involved interviews with key activists and an archival analysis of documents at the George Padmore Institute. Political blackness is based on an inaccurate understanding of the relationship between multiculturalism and anti-racism; a misreading of the complex and global nature of racism and a non-strategic essentialism. The concept also creates a form non-whiteism, which disempowers ethnic minority communities and works to delegitimize African Diasporic Blackness, which has a tradition of resisting racist oppression.     

Chemically induced degradation of CK2 by proteolysis targeting chimeras based on a ubiquitin–proteasome pathway

As a ubiquitous, highly pleiotropic and constitutively active serine/threonine protein kinase, casein kinase 2 (CK2) is closely associated with tumorigenesis by its overexpression in cancer cells. Here we report several proteolysis targeting chimeras (PROTACs) via “click reaction” to connect a CK2 inhibitor (CX-4945) and pomalidomide for degradation of CK2 protein. Among them, compound 2 degraded CK2 in a dose and time-dependent manner, and kept CK2 at a low basal level by recruiting ubiquitin-proteasome system. The degradation of CK2 resulted in the reduced phosphorylation of Akt and the up-regulation of p53. As a CK2 protein degrader, 2 showed the analogous cytotoxicity to CX-4945 but with a quite different mechanism of action from the CK2 inhibitor, hinting that degradation of CK2 proteins by PROTACs is a potential way for cancer treatments.