Using 3D infrared (IR) exchange spectroscopy, the ultrafast hydrogenbond forming and breaking (i.e., complexation) kinetics of phenol to benzene in a benzene/CCl 4 mixture is investigated. By introducing a third time point at which the hydrogen-bonding state of phenol is measured (in comparison with 2D IR exchange spectroscopy), the spectroscopic method can serve as a critical test of whether the spectroscopic coordinate used to observe the exchange process is a memory-free, or Markovian, coordinate. For the system under investigation, the 3D IR results suggest that this is not the case. This conclusion is reconfirmed by accompanying molecular dynamics simulations, which furthermore reveal that the non-Markovian kinetics is caused by the heterogeneous structure of the mixed solvent.3D IR spectroscopy | solvent dynamics | ultrafast dynamics W henever one writes a chemical reaction equation, such as in the simplest case of an equilibrium between two states of a molecular systemwith the corresponding Master equation for its kineticsone implicitly assumes Markovianity. That is, it is assumed that the probability to react per time unit, e.g., from C to F, scales linearly with concentration [C] with proportionality constant k CF , but does not depend on the history of how C has been formed. When the reaction is slow in comparison with the relaxation of its environment, then this assumption is well justified. One can however think of many situations where this is not the case. For example, proteins are heterogeneous on very long timescales due to their structural complexity, so enzymatic reaction catalyzed by them might not fulfill that condition (1). Other examples are found in glass-forming liquids close to the glass transition, when their relaxation covers many orders of magnitude in time (2). When the speed of a reaction approaches the ultrafast picosecond regime, which is the topic of the present paper, then even the solvation time of normal liquids far away from any glass transition may become time-limiting. For example, it has been shown that the distance between a Na + and a Cl − ion is not a good reaction coordinate to describe ion pair dissociation in aqueous solution (3), in the sense that the distance for which the free energy peaks does not correspond with the transition state of the reaction. Hidden coordinates exist, which must be solvent coordinates because there are no other degrees of freedom. Unless these solvent coordinates have not fully relaxed and lost their memory about a reaction event, the probability for a back reaction must depend on the history. Markovianity is related to a separation of timescales between the speed of a chemical reaction of a molecular system versus that of the relaxation of its solvent. Often, a separation of timescales goes hand-in-hand with a separation of solute and solvent, but such a system-bath approach fails for ultrafast reactions.It is important to recognize that the question of Markovianity is not an intrinsic property of a chemical process, but rather is relate...

We utilize two-color two-dimensional infrared spectroscopy to measure the intermolecular coupling between azide ions and their surrounding water molecules in order to gain information about the nature of hydrogen bonding of water to ions. Our findings indicate that the main spectral contribution to the intermolecular cross-peak comes from population transfer between the asymmetric stretch vibration of azide and the OD-stretch vibration of D2O. The azide-bound D2O bleach/stimulated emission signal, which is spectrally much narrower than its linear absorption spectrum, shows that the experiment is selective to solvation shell water molecules for population times up to 500 fs. The waters around the ion are present in an electrostatically better defined environment. Afterwards, 1 ps, the sample thermalizes and selectivity is lost. On the other hand, the excited state absorption signal of the azide-bound D2O is much broader. The asymmetry in spectral width between bleach/stimulated emission versus excited absorption has been observed in very much the same way for isotope-diluted ice Ih, where it has been attributed to the anharmonicity of the OD potential. Azide-water intermolecular coupling measured by two-color two-dimensional infrared spectroscopy We utilize two-color two-dimensional infrared spectroscopy to measure the intermolecular coupling between azide ions and their surrounding water molecules in order to gain information about the nature of hydrogen bonding of water to ions. Our findings indicate that the main spectral contribution to the intermolecular cross-peak comes from population transfer between the asymmetric stretch vibration of azide and the OD-stretch vibration of D 2 O. The azide-bound D 2 O bleach/stimulated emission signal, which is spectrally much narrower than its linear absorption spectrum, shows that the experiment is selective to solvation shell water molecules for population times up to ∼500 fs. The waters around the ion are present in an electrostatically better defined environment. Afterwards, ∼1 ps, the sample thermalizes and selectivity is lost. On the other hand, the excited state absorption signal of the azide-bound D 2 O is much broader. The asymmetry in spectral width between bleach/stimulated emission versus excited absorption has been observed in very much the same way for isotope-diluted ice Ih, where it has been attributed to the anharmonicity of the OD potential.

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We would like to thank EastCHEM and the School of Chemistry of UoE for funding. We are also very grateful to Professor E. Campbell and her workgroup for the opportunity to work on Raman and AFM instruments and for fruitful advice. Supporting information:Additional information available free of charge via the internet at http://pubs.acs.org/ Keywords: SERS; nanoshell; peptide; redox; Goodpasture's; proteolysis AbstractWe describe a novel surface enhanced Raman spectroscopy (SERS) sensing approach utilizing AuroshellTM gold Nanoshells and demonstrate its application to analysis of critical redox-potential dependent changes in antigen structure that are implicated in the initiation of a human autoimmune disease. In Goodpasture's disease, an autoimmune reaction is thought to arise from incomplete proteolysis of the autoantigen, α3(IV)NC1(67-85) by proteases including Cathepsin D. We have used SERS to study conformational changes in the antigen that correlate with its oxidation state and toshow that the antigen must be in the reduced state in order to undergo proteolysis. Our approach determined that an intracellular redox-potential of ~-200 mV was sufficient for reduction, prerequisite for productive processing, of the intratramolecular disulfide bond within the antigenic fragment α3(IV)NC1 67-85 . Moreover we demonstrate that interaction of the antigenic fragment with Cathepsisn D, is vastly facilitated by reduction of this disulfide bond and that the peptide bonds subsequently cleaved by Cathepsisn D can be identified by consultation of a SERS library of short synthetic peptides.

PRACE ORYGINALNEprace oryginalneo riginal papers STRESZCZENIE Wstęp. Dzieci z problemami neurologicznymi zazwyczaj prezentują zaburzenia posturalne, motoryczne i dysfunkcje w zakresie aktywności życia codziennego, w tym w zakresie jedzenia. Jednakże mięśnie narządu żucia rzadko podlegają ocenie. Cel. Ocena jakie trudności mają dzieci z zaburzeniami neurologicznymi w czasie funkcji jedzenia oraz ocena mięśni narządu żucia. Materiał i metody. W badaniu pilotażowym dokonaliśmy oceny 19 dzieci (średnia wieku 6,3 ± 1,4 lat) z zaburzeniami neurorozwojowymi i problemami z jedzeniem. Badania uzyskały zgodę Komisji Bioetycznej przy Uniwersytetecie Medycznym im. Karola Marcinkowskiego w Poznaniu (339/15, 9.04.2015). Rozwój ruchowy został zbadany przy użyciu Gross Motor Function Measure -88. Funkcje jedzenia zostały zbadane za pomocą kwestionariusza Castillo-Morales. Postawa ciała została oceniona za pomocą Wzrokowej Oceny Postawy Ciała Metodą Kasperczyka.Wyniki. Istnieje korelacja pomiędzy funkcją ssania-połykania a napięciem mięśni mostkowo-obojczykowo-sutkowatych (p = 0,032) i czworobocznego grzbietu (p = 0,01766). Istnieje korelacja pomiędzy ślinieniem się a napięciem takich mięśni, jak: mięsień prosty głowy tylny mniejszy (Chi 2 Pearsona, p = 0,027) i skroniowy (p = 0,04801). Dzieci z zaburzeniami neurologicznymi zazwyczaj jedzą pokarmy o konsystencji płynnej lub półpłynnej, jeśli mają przykurcz w obszarze mięśni: żwaczy (p = 0,01766), mostkowo-obojczykowo-sutkowatego (p = 0,046), pochyłego przedniego (p = 0,04664), zębatego przedniego (p = 0,03470), czworobocznego grzbietu (p = 0,02688). Wnioski. Hipertonus mięśni może powodować zaburzenia w zakresie funkcji jedzenia, powodując nadmierne ślinienie się bądź wpływając na brak umiejętności jedzenia o stałej konsystencji. Dzieci z zaburzeniami neurologicznymi mają skrócone mięśnie narządu żucia, zwłaszcza mięsień mostkowo-obojczykowo-sutkowy, pochyły przedni, czworboczny grzbietu, zębaty przedni, prosty głowy tylny mniejszy, żwacz, skroniowy.