Wrapping the alpha-crystallin domain fold in a chaperone assembly

Small heat shock proteins (sHsps) are oligomers that perform a protective function by binding denatured proteins. Although ubiquitous, they are of variable sequence except for a C-terminal similar to 90-residue "alpha-crystallin domain". Unlike larger stress response chaperones, sHsps are ATP-independent and generally form polydisperse assemblies. One proposed mechanism of action involves these assemblies breaking into smaller subunits in response to stress, before binding unfolding substrate and reforming into larger complexes. Two previously solved non-metazoan sHsp multimers are built from dimers formed by domain swapping between the alpha-crystallin domains,. adding to evidence that the smaller subunits are dimers. Here, the 2.5 angstrom resolution structure of an sHsp from the parasitic flatworm Taenia saginata Tsp36, the first metazoan crystal structure, shows a new mode of dimerization involving N-terminal regions, which differs from that seen for non-metazoan sHsps. Sequence differences in the a-crystallin domains between metazoans and nonmetazoans are critical to the different mechanism of dimerization, suggesting that some structural features seen for Tsp36 may be generalized to other metazoan sHsps. The structure also indicates scope for flexible assembly of subunits, supporting the proposed process of oligomer breakdown, substrate binding and reassembly as the chaperone mechanism. It further shows how sHsps can bind coil and secondary structural elements by wrapping them around the alpha-crystallin domain. The structure also illustrates possible roles for conserved residues associated with disease, and suggests a mechanism for the sHsp-related pathogenicity of some flatworm infections. Tsp36, like other flatworm sHsps, possesses two divergent sHsp repeats per monomer. Together with the two previously solved structures, a total of four alpha-crystallin domain structures are now available, giving a better definition of domain boundaries for sHsps

Relative Reaktivität Alkyl-substituierter Alkene und Cycloalkene gegenüber Diarylcarbenium-Ionen

Nach der Konkurrenzmethode wurden die relativen Reaktivitäten Alkyl-substituierter Alkene 4 gegenüber Diarylmethyl-Kationen 2 bestimmt, die in Gegenwart von Alken-Gemischen aus Diarylmethylchloriden 1 und Lewis-Säuren erzeugt wurden. Die Konkurrenz-konstanten werden durch die Art der Lewis-Säure nur wenig beeinflußt, so daß eine eventuelle Differenz der freien Solvatationsenthalpie verschiedener aktivierter Komplexe von der Natur des Gegenions unabhängig sein muß. Aus der 6-50fachen Reaktionsbeschleunigung durch Methylgruppen, die sich am angegriffenen Alken-Kohlenstoff befinden und der 104fachen Reaktivitätssteigerung durch Methylgruppen am neuen Carbeniumzentrum wird auf einen wenig verbrückten Übergangszustand geschlossen

Photooxygenation mechanisms in naproxen-amino acid linked systems

The photooxygenation of model compounds containing the two enantiomers of naproxen (NPX) covalently linked to histidine (His), tryptophan (Trp) and tyrosine (Tyr) has been investigated by steady state irradiation, fluorescence spectroscopy and laser flash photolysis. The NPX–His systems presented the highest oxygen-mediated photoreactivity. Their fluorescence spectra matched that of isolated NPX and showed a clear quenching by oxygen, leading to a diminished production of the NPX triplet excited state ( 3 NPX*–His). Analysis of the NPX–His and NPX–Trp photolysates by UPLC-MS–MS revealed in both cases the formation of two photoproducts, arising from the reaction of singlet oxygen (1 O2) with the amino acid moiety. The most remarkable feature of NPX–Trp systems was a fast and stereoselective intramolecular fluorescence quenching, which prevented the efficient formation of 3 NPX*–Trp, thus explaining their lower reactivity towards photooxygenation. Finally, the NPX–Tyr systems were nearly unreactive and exhibited photophysical properties essentially coincident with those of the parent NPX. Overall, these results point to a type II photooxygenation mechanism, triggered by generation of 1 O2 from the 3 NPX* chromophoreFinancial support from the Spanish Government (CTQ2010-14882, JCI-2011-09926, Miguel Servet CP11/00154), from the EU (PCIG12-GA-2012-334257), from the Universitat Politecnica de Valencia (SP20120757) and from the Conselleria de Educacio, cultura i Esport (PROMETEOII/2013/005, GV/2013/051) is gratefully acknowledged.Vayá Pérez, I.; Andreu Ros, MI.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Photooxygenation mechanisms in naproxen-amino acid linked systems. Photochemical & Photobiological Sciences Photochemical and Photobiological Sciences. 13:224-230. https://doi.org/10.1039/c3pp50252jS22423013L. I. Grossweiner and K. C.Smith, Photochemistry, in The Science of Photobiology, ed. K. C. Smith, Plenum Press, New York, 2nd edn, 1989, pp. 47–78L. Pretali and A.Albini, in CRC Handbook of Organic Photochemistry and Photobiology, ed. A. Griesbeck, M. Oelgemöller and F. Ghetti, CRC Press, Boca Raton, FL, 3rd edn, 2012, pp. 369–391Foote, C. S. (1991). DEFINITION OF TYPE I and TYPE II PHOTOSENSITIZED OXIDATION. Photochemistry and Photobiology, 54(5), 659-659. doi:10.1111/j.1751-1097.1991.tb02071.xDavies, M. J. (2003). Singlet oxygen-mediated damage to proteins and its consequences. Biochemical and Biophysical Research Communications, 305(3), 761-770. doi:10.1016/s0006-291x(03)00817-9Davies, M. J. (2004). Reactive species formed on proteins exposed to singlet oxygen. Photochemical & Photobiological Sciences, 3(1), 17. doi:10.1039/b307576cGirotti, A. W. (2001). Photosensitized oxidation of membrane lipids: reaction pathways, cytotoxic effects, and cytoprotective mechanisms. Journal of Photochemistry and Photobiology B: Biology, 63(1-3), 103-113. doi:10.1016/s1011-1344(01)00207-xAndreu, I., Morera, I. M., Boscá, F., Sanchez, L., Camps, P., & Miranda, M. A. (2008). Cholesterol–diaryl ketone stereoisomeric dyads as models for «clean» type I and type II photooxygenation mechanisms. Organic & Biomolecular Chemistry, 6(5), 860. doi:10.1039/b718068cStadtman, E. R. (1993). Oxidation of Free Amino Acids and Amino Acid Residues in Proteins by Radiolysis and by Metal-Catalyzed Reactions. Annual Review of Biochemistry, 62(1), 797-821. doi:10.1146/annurev.bi.62.070193.004053Garrison, W. M. (1987). Reaction mechanisms in the radiolysis of peptides, polypeptides, and proteins. Chemical Reviews, 87(2), 381-398. doi:10.1021/cr00078a006P. U. Giacomoni , Sun Protection in Man, Comprehensive Series in Photosciences, Elsevier, Amsterdam, 2001, vol. 3R. C. Straight and J. D.Spikes, Photosensitized oxidation of biomolecules. in Polymers and Biopolymers, ed. A. A. Frimer and O. Singlet, CRC Press, Boca Raton, FL, 1985, pp. 91–143Wright, A., Bubb, W. A., Hawkins, C. L., & Davies, M. J. (2002). Singlet Oxygen–mediated Protein Oxidation: Evidence for the Formation of Reactive Side Chain Peroxides on Tyrosine Residues¶. Photochemistry and Photobiology, 76(1), 35. doi:10.1562/0031-8655(2002)0762.0.co;2Agon, V. V., Bubb, W. A., Wright, A., Hawkins, C. L., & Davies, M. J. (2006). Sensitizer-mediated photooxidation of histidine residues: Evidence for the formation of reactive side-chain peroxides. Free Radical Biology and Medicine, 40(4), 698-710. doi:10.1016/j.freeradbiomed.2005.09.039Huyett, J. E., Doan, P. E., Gurbiel, R., Houseman, A. L. P., Sivaraja, M., Goodin, D. B., & Hoffman, B. M. (1995). Compound ES of Cytochrome c Peroxidase Contains a Trp .pi.-Cation Radical: Characterization by Continuous Wave and Pulsed Q-Band External Nuclear Double Resonance Spectroscopy. Journal of the American Chemical Society, 117(35), 9033-9041. doi:10.1021/ja00140a021Redmond, R. W., & Gamlin, J. N. (1999). A Compilation of Singlet Oxygen Yields from Biologically Relevant Molecules. Photochemistry and Photobiology, 70(4), 391-475. doi:10.1111/j.1751-1097.1999.tb08240.xA. J. Lewis and D. E.Furst, Nonsteroidal Anti-Inflammatory Drugs: Mechanisms and Clinical Uses, Marcel Dekker, New York, 2nd edn, 1994Boscá, F., Marín, M. L., & Miranda, M. A. (2001). Photoreactivity of the Nonsteroidal Anti-inflammatory 2-Arylpropionic Acids with Photosensitizing Side Effects¶. Photochemistry and Photobiology, 74(5), 637. doi:10.1562/0031-8655(2001)0742.0.co;2Beijersbergen van Henegouwen, G. M. J. (1991). New trends in photobiology. Journal of Photochemistry and Photobiology B: Biology, 10(3), 183-210. doi:10.1016/1011-1344(91)85002-xMiranda, M. A., Castell, J. V., Hernández, D., Gómez-Lechón, M. J., Bosca, F., Morera, I. M., & Sarabia, Z. (1998). Drug-Photosensitized Protein Modification:  Identification of the Reactive Sites and Elucidation of the Reaction Mechanisms with Tiaprofenic Acid/Albumin as Model System†. Chemical Research in Toxicology, 11(3), 172-177. doi:10.1021/tx970082dJiménez, M. C., Pischel, U., & Miranda, M. A. (2007). Photoinduced processes in naproxen-based chiral dyads. Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 8(3), 128-142. doi:10.1016/j.jphotochemrev.2007.10.001Catalfo, A., Bracchitta, G., & De Guidi, G. (2009). Role of aromatic amino acid tryptophan UVA-photoproducts in the determination of drug photosensitization mechanism: a comparison between methylene blue and naproxen. Photochemical & Photobiological Sciences, 8(10), 1467. doi:10.1039/b9pp00028cVayá, I., Pérez-Ruiz, R., Lhiaubet-Vallet, V., Jiménez, M. C., & Miranda, M. A. (2010). Drug–protein interactions assessed by fluorescence measurements in the real complexes and in model dyads. Chemical Physics Letters, 486(4-6), 147-153. doi:10.1016/j.cplett.2009.12.091Vayá, I., Jiménez, M. C., & Miranda, M. A. (2007). Excited-State Interactions in Flurbiprofen−Tryptophan Dyads. The Journal of Physical Chemistry B, 111(31), 9363-9371. doi:10.1021/jp071301zVayá, I., Bonancía, P., Jiménez, M. C., Markovitsi, D., Gustavsson, T., & Miranda, M. A. (2013). Excited state interactions between flurbiprofen and tryptophan in drug–protein complexes and in model dyads. Fluorescence studies from the femtosecond to the nanosecond time domains. Physical Chemistry Chemical Physics, 15(13), 4727. doi:10.1039/c3cp43847cGriesbeck, A. G., Neudörfl, J., & de Kiff, A. (2011). Photoinduced electron-transfer chemistry of the bielectrophoric N-phthaloyl derivatives of the amino acids tyrosine, histidine and tryptophan. Beilstein Journal of Organic Chemistry, 7, 518-524. doi:10.3762/bjoc.7.60Giese, B., Wang, M., Gao, J., Stoltz, M., Müller, P., & Graber, M. (2009). Electron Relay Race in Peptides. The Journal of Organic Chemistry, 74(10), 3621-3625. doi:10.1021/jo900375fCordes, M., Köttgen, A., Jasper, C., Jacques, O., Boudebous, H., & Giese, B. (2008). Influence of Amino Acid Side Chains on Long-Distance Electron Transfer in Peptides: Electron Hopping via «Stepping Stones». Angewandte Chemie International Edition, 47(18), 3461-3463. doi:10.1002/anie.200705588Abraham, B., & Kelly, L. A. (2003). Photooxidation of Amino Acids and Proteins Mediated by Novel 1,8-Naphthalimide Derivatives. The Journal of Physical Chemistry B, 107(45), 12534-12541. doi:10.1021/jp0358275Cadenas, E. (1989). Biochemistry of Oxygen Toxicity. Annual Review of Biochemistry, 58(1), 79-110. doi:10.1146/annurev.bi.58.070189.000455Peña, D., Martí, C., Noneil, S., Martínez, L. A., & Miranda, M. A. (1997). Time-Resolved Near Infrared Studies on Singlet Oxygen Production by the Photosensitizing 2-Arylpropionic Acids. Photochemistry and Photobiology, 65(5), 828-832. doi:10.1111/j.1751-1097.1997.tb01930.xKerwin, B. A., & Remmele, R. L. (2007). Protect from Light: Photodegradation and Protein Biologics. Journal of Pharmaceutical Sciences, 96(6), 1468-1479. doi:10.1002/jps.20815Kang, P., & Foote, C. S. (2000). Synthesis of a 13C,15N labeled imidazole and characterization of the 2,5-endoperoxide and its decomposition. Tetrahedron Letters, 41(49), 9623-9626. doi:10.1016/s0040-4039(00)01731-7Saito, I., Matsuura, T., Nakagawa, M., & Hino, T. (1977). Peroxidic intermediates in photosensitized oxygenation of tryptophan derivatives. Accounts of Chemical Research, 10(9), 346-352. doi:10.1021/ar50117a00

MicroRNA-21 dysregulates the expression of MEF2C in neurons in monkey and human SIV/HIV neurological disease

MicroRNAs (miRNAs) have important roles in regulating a plethora of physiological and pathophysiogical processes including neurodegeneration. In both human immunodeficiency virus (HIV)-associated dementia in humans and its monkey model simian immunodeficiency virus encephalitis (SIVE), we find miR-21, a miRNA largely known for its link to oncogenesis, to be significantly upregulated in the brain. In situ hybridization of the diseased brain sections revealed induction of miR-21 in neurons. miR-21 can be induced in neurons by prolonged N-methyl--aspartic acid receptor stimulation, an excitotoxic process active in HIV and other neurodegenerative diseases. Introduction of miR-21 into human neurons leads to pathological functional defects. Furthermore, we show that miR-21 specifically targets the mRNA of myocyte enhancer factor 2C (MEF2C), a transcription factor crucial for neuronal function, and reduces its expression. MEF2C is dramatically downregulated in neurons of HIV-associated dementia patients, as well as monkeys with SIVE. Together, this study elucidates a novel role for miR-21 in the brain, not only as a potential signature of neurological disease, but also as a crucial effector of HIV-induced neuronal dysfunction and neurodegeneration

Source localization of reaction-diffusion models for brain tumors

We propose a mathematically well-founded approach for locating the source (initial state) of density functions evolved within a nonlinear reaction-diffusion model. The reconstruction of the initial source is an ill-posed inverse problem since the solution is highly unstable with respect to measurement noise. To address this instability problem, we introduce a regularization procedure based on the nonlinear Landweber method for the stable determination of the source location. This amounts to solving a sequence of well-posed forward reaction-diffusion problems. The developed framework is general, and as a special instance we consider the problem of source localization of brain tumors. We show numerically that the source of the initial densities of tumor cells are reconstructed well on both imaging data consisting of simple and complex geometric structures

Determinants of female sexual function in inflammatory bowel disease: a survey based cross-sectional analysis

<p>Abstract</p> <p>Background</p> <p>Sexual function is impaired in women with inflammatory bowel disease (IBD) as compared to normal controls. We examined disease specific determinants of different aspects of low sexual function.</p> <p>Methods</p> <p>Women with IBD aged 18 to 65 presenting to the university departments of internal medicine and surgery were included. In addition, a random sample from the national patients organization was used (separate analyses). Sexual function was assessed by the Brief Index of Sexual Function in Women, comprising seven different domains of sexuality. Function was considered impaired if subscores were < -1 on a z-normalized scale. Results are presented as age adjusted odds ratios with 95% CI based on multiple logistic regression.</p> <p>Results</p> <p>336 questionnaires were included (219 Crohn's disease, 117 ulcerative colitis). Most women reported low sexual activity (63%; 17% none at all, 20% moderate or high activity). Partnership satisfaction was high in spite of low sexual interest in this group. Depressed mood was the strongest predictor of low sexual function scores in all domains. Urban residency and higher socioecomic status had a protective effect. Disease activity was moderately associated with low desire (OR 1.8, 95% CI 1.0 to 3.2). Severity of the disease course impacted most on intercourse frequency (OR 2.3, 95% CI 1.4 to 4.7). Lubrication problems were more common in smokers (OR 2.5, 95% CI 1.3 to 5.1).</p> <p>Conclusion</p> <p>Mood disturbances and social environment impacted more on sexual function in women with IBD than disease specific factors. Smoking is associated with lubrication problems.</p

Charge Transport in DNA-Based Devices

Charge migration along DNA molecules has attracted scientific interest for over half a century. Reports on possible high rates of charge transfer between donor and acceptor through the DNA, obtained in the last decade from solution chemistry experiments on large numbers of molecules, triggered a series of direct electrical transport measurements through DNA single molecules, bundles and networks. These measurements are reviewed and presented here. From these experiments we conclude that electrical transport is feasible in short DNA molecules, in bundles and networks, but blocked in long single molecules that are attached to surfaces. The experimental background is complemented by an account of the theoretical/computational schemes that are applied to study the electronic and transport properties of DNA-based nanowires. Examples of selected applications are given, to show the capabilities and limits of current theoretical approaches to accurately describe the wires, interpret the transport measurements, and predict suitable strategies to enhance the conductivity of DNA nanostructures.Comment: A single pdf file of 52 pages, containing the text and 23 figures. Review about direct measurements of DNA conductivity and related theoretical studies. For higher-resolution figures contact the authors or retrieve the original publications cited in the caption