We report the first vibrational circular dichroism (VCD) measurement of spatial heterogeneity in a sample using infrared (IR) microsampling. Vibrational circular dichroism spectra are typically measured using a standard IR cell with an IR beam diameter of 10 mm or greater making it impossible to investigate the spatial heterogeneity of a solid film sample. We have constructed a VCD sampling assembly with either 3 mm or 1 mm spatial resolution. An XY-translation stage was used to measure spectra at different spatial locations producing IR and VCD maps of the sample. In addition, a rotating sample stage was employed using a dual photoelastic modulator (PEM) setup to suppress artifacts due to linear birefringence in solid-phase or film samples. Infrared and VCD mapping of an insulin fibril film has been carried out at both 3 and 1 mm spatial resolution, and lysozyme films were mapped at 1 mm resolution. The IR spectra of different spots vary in intensity due primarily to sample thickness. The changes in the VCD intensity across the map largely correlate to corresponding changes in the IR map. Closer inspection of the insulin map revealed changes in the relative intensities of the VCD spectra not present in the parent IR spectra, which indicated differences in the degree of supramolecular chirality of the fibrils in the various spatial regions. For lysozyme films, in addition to different degrees of supramolecular chirality, reversal of the net fibril chirality was observed. The large signal-to-noise ratio observed at 1 mm resolution implies the feasibility of further increasing the spatial resolution by one or two orders of magnitude for protein fibril film samples.

• MeSH
• amyloid analýza   chemie   MeSH
• artefakty MeSH
• cirkulární dichroismus metody   MeSH
• inzulin analýza   chemie   MeSH
• muramidasa analýza   chemie   MeSH
• počítačové zpracování signálu MeSH
• skot MeSH
• spektroskopie infračervená s Fourierovou transformací MeSH
• vibrace MeSH
• zvířata MeSH
• Check Tag
• skot MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

• MeSH
• azidy MeSH
• cirkulární dichroismus metody   MeSH
• kyanidy MeSH
• metmyoglobin analýza   chemie   MeSH

Recently, we have found that thermal stability of photosystem II (PSII) photochemistry in spruce needles is higher than in other plants (barley, beech) cultivated under the same temperatures. In this work, temperature dependences of various characteristics of PSII organization were studied in order to obtain complex information on the thermal stability of PSII function and organization in spruce. Temperature dependency of circular dichroism spectra revealed by about 6 °C higher thermal stability of macrodomain organization in spruce thylakoid membranes in comparison with Arabidopsis and barley ones; however, thermal disintegration of light-harvesting complex of PSII did not significantly differ among the species studied. These results thus indicate that thermal stability of PSII macro-organization in spruce thylakoid membranes is enhanced to a similar extent as thermal stability of PSII photochemistry. Clear-native polyacrylamide gel electrophoresis of preheated thylakoids demonstrated that among the separated pigment-protein complexes, only PSII supercomplexes (SCs) revealed considerably higher thermal stability in spruce thylakoids as compared to Arabidopsis and barley ones. Hence we suggest that higher thermal stability of PSII macro-organization of spruce is influenced by the maintenance of PSII SCs in the thylakoid membrane. In addition, we discuss possible effects of different PSII organizations and lipid compositions on the thermal stability of spruce thylakoid membranes.

• MeSH
• Arabidopsis cytologie   fyziologie   MeSH
• chlorofyl fyziologie   MeSH
• cirkulární dichroismus MeSH
• elektroforéza v polyakrylamidovém gelu MeSH
• fluorescence MeSH
• fotosystém II (proteinový komplex) fyziologie   MeSH
• ječmen (rod) cytologie   fyziologie   MeSH
• smrk cytologie   fyziologie   MeSH
• tylakoidy fyziologie   MeSH
• vysoká teplota MeSH
• Publikační typ
• časopisecké články MeSH
• srovnávací studie MeSH

The interactions of poly-L-glutamic acid and a cationic porphyrin derivative in aqueous solutions were studied by the combination of vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectroscopies. It was found that non-covalent interactions between both agents influence the structure of the polymeric matrix and the guest porphyrins and vice versa, but the physico-chemical properties of the solutions, especially the pH and the relative permittivity of the solvent, play a key role in the structure of the polypeptide part of the formed complexes. It was shown that the interaction with porphyrins prevents the precipitation of poly-L-glutamic acid in aqueous solution at acidic pH. In special conditions, the porphyrins attached to the polypeptide probably possess face-to-face interaction as demonstrated by the enhancement of the characteristic ECD signal and the appearance of sidebands on its short and long wavelength sides. Copyright 2005 European Peptide Society and John Wiley & Sons, Ltd.

• MeSH
• cirkulární dichroismus MeSH
• financování organizované MeSH
• kyselina polyglutamová chemie   MeSH
• molekulární struktura MeSH
• porfyriny chemie   MeSH
• roztoky MeSH
• spektrofotometrie ultrafialová MeSH
• voda chemie   MeSH

An increased circular dichroism (CD) signal of large molecular aggregates formed upon DNA condensation was observed a long time ago, and is often referred to as psi-CD. The effort to understand this phenomenon is further motivated by the latest DNA packing studies and advances in macromolecular chemistry. In the present work, the transition dipole coupling model describing interactions of molecules with light has been extended to handle systems of arbitrary size. The analytical formulae obtained retain the simplicity and computational speed of the standard approach. The origin of the psi-effect was investigated on several model systems. The results suggest that the CD enhancement is primarily caused by delocalized phonon-like excitations in nucleic acid strands. The size of the system exhibiting the effect thus does not need to be comparable with or greater than the wavelength of the absorbed light. Small structural irregularities still allow for the enhancement while a larger disorder breaks it. The modeling is consistent with previous experimental electronic and vibrational CD studies, and makes it possible to correlate the enhancement with the geometry of the nucleic acid systems. 2008 Wiley Periodicals, Inc.

• MeSH
• akustika MeSH
• biologické hodiny MeSH
• cirkulární dichroismus metody   MeSH
• dimerizace MeSH
• DNA chemie   MeSH
• financování organizované MeSH
• molekulární modely MeSH
• vibrace MeSH

Oxidative stress can lead to various derivatives of the tyrosine residue in peptides and proteins. A typical product is 3-nitro-L-tyrosine residue (Nit), which can affect protein behavior during neurodegenerative processes, such as those associated with Alzheimer's and Parkinson's diseases. Surface enhanced Raman spectroscopy (SERS) is a technique with potential for detecting peptides and their metabolic products at very low concentrations. To explore the applicability to Nit, we use SERS to monitor tyrosine nitration in Met-Enkephalin, rev-Prion protein, and α-synuclein models. Useful nitration indicators were the intensity ratio of two tyrosine marker bands at 825 and 870 cm-1 and a bending vibration of the nitro group. During the SERS measurement, a conversion of nitrotyrosine to azobenzene containing peptides was observed. The interpretation of the spectra has been based on density functional theory (DFT) simulations. The CAM-B3LYP and ωB97XD functionals were found to be most suitable for modeling the measured data. The secondary structure of the α-synuclein models was monitored by electronic and vibrational circular dichroism (ECD and VCD) spectroscopies and modeled by molecular dynamics (MD) simulations. The results suggest that the nitration in these peptides has a limited effect on the secondary structure, but may trigger their aggregation.

• MeSH
• azosloučeniny chemie   MeSH
• cirkulární dichroismus MeSH
• peptidy chemická syntéza   chemie   MeSH
• Ramanova spektroskopie metody   MeSH
• sekundární struktura proteinů MeSH
• simulace molekulární dynamiky MeSH
• teorie funkcionálu hustoty MeSH
• tyrosin analogy a deriváty   analýza   MeSH
• Publikační typ
• časopisecké články MeSH

We report that 3',5'-cyclic CMP undergoes nonenzymatic di- and trimerization at 20 °C under dry conditions upon proton or UV irradiation. The reaction involves stacking of the cyclic monomers and subsequent polymerization through serial transphosphorylations between the stacked monomers. Proton- and UV-induced oligomerization of 3',5'-cyclic CMP demonstrates that pyrimidines-similar to purines-might also have taken part in the spontaneous generation of RNA under plausible prebiotic conditions as well as in an extraterrestrial context. The observed polymerization of naturally occurring 3',5'-cyclic nucleotides supports the possibility that the extant genetic nucleic acids might have originated by way of a straight Occamian path, starting from simple reactions between plausibly preactivated monomers.

• MeSH
• chemické modely MeSH
• cirkulární dichroismus MeSH
• CMP cyklický chemie   účinky záření   MeSH
• evoluce chemická MeSH
• oligoribonukleotidy chemická syntéza   MeSH
• polymerizace MeSH
• protony MeSH
• RNA chemická syntéza   MeSH
• spektrometrie hmotnostní - ionizace laserem za účasti matrice MeSH
• ultrafialové záření MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Light-harvesting complex II (LHCII) from the marine green macroalga Bryopsis corticulans is spectroscopically characterized to understand the structural and functional changes resulting from adaptation to intertidal environment. LHCII is homologous to its counterpart in land plants but has a different carotenoid and chlorophyll (Chl) composition. This is reflected in the steady-state absorption, fluorescence, linear dichroism, circular dichroism and anisotropic circular dichroism spectra. Time-resolved fluorescence and two-dimensional electronic spectroscopy were used to investigate the consequences of this adaptive change in the pigment composition on the excited-state dynamics. The complex contains additional Chl b spectral forms - absorbing at around 650 nm and 658 nm - and lacks the red-most Chl a forms compared with higher-plant LHCII. Similar to plant LHCII, energy transfer between Chls occurs on timescales from under hundred fs (mainly from Chl b to Chl a) to several picoseconds (mainly between Chl a pools). However, the presence of long-lived, weakly coupled Chl b and Chl a states leads to slower exciton equilibration in LHCII from B. corticulans. The finding demonstrates a trade-off between the enhanced absorption of blue-green light and the excitation migration time. However, the adaptive change does not result in a significant drop in the overall photochemical efficiency of Photosystem II. These results show that LHCII is a robust adaptable system whose spectral properties can be tuned to the environment for optimal light harvesting.

• MeSH
• časové faktory MeSH
• Chlorophyta metabolismus   MeSH
• cirkulární dichroismus MeSH
• fluorescenční spektrometrie MeSH
• přenos energie * MeSH
• světlosběrné proteinové komplexy metabolismus   MeSH
• teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Aggregation of the neuronal protein α-synuclein into amyloid fibrils plays a central role in the development of Parkinson's disease. Growth of fibrils can be suppressed by blocking fibril ends from their interaction with monomeric proteins. In this work, we constructed inhibitors that bind to the ends of α-synuclein amyloid fibrils with very high affinity. They are based on synthetic α-synuclein dimers and interact with fibrils via two monomeric subunits adopting conformation that efficiently blocks fibril elongation. By tuning the charge of dimers, we further enhanced the binding affinity and prepared a construct that inhibits fibril elongation at nanomolar concentration (IC50 ≈ 20 nM). To the best of our knowledge, it is the most efficient inhibitor of α-synuclein fibrillization.

• MeSH
• alfa-synuklein antagonisté a inhibitory   genetika   metabolismus   MeSH
• amyloid antagonisté a inhibitory   chemie   metabolismus   MeSH
• cirkulární dichroismus MeSH
• disulfidy chemie   MeSH
• látky ovlivňující centrální nervový systém chemie   farmakologie   MeSH
• lidé MeSH
• multimerizace proteinu MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• MeSH
• amyloidní plaky MeSH
• amyloidóza etiologie   MeSH
• cirkulární dichroismus MeSH
• elektronová paramagnetická rezonance MeSH
• lidé MeSH
• neurodegenerativní nemoci etiologie   MeSH
• prealbumin MeSH
• sbalování proteinů MeSH
• spektrometrie hmotnostní - ionizace laserem za účasti matrice MeSH
• transferin MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• recenze MeSH