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The receptorial responsiveness method (RRM) enables the estimation of a change in concentration of an (even degradable) agonist, near its receptor, via curve fitting to (at least) two concentration-effect (E/c) curves of a stable agonist. One curve should be generated before this change, and the other afterwards, in the same system. It follows that RRM yields a surrogate parameter ("cx") as the concentration of the stable agonist being equieffective with the change in concentration of the other agonist. However, regression can be conducted several ways, which can affect the accuracy, precision and ease-of-use. This study utilized data of previous ex vivo investigations. Known concentrations of stable agonists were estimated with RRM by performing individual (local) or global fitting, this latter with one or two model(s), using a logarithmic (logcx) or a nonlogarithmic (cx) parameter (the latter in a complex or in a simplified equation), with ordinary least-squares or robust regression, and with an "allat-once" or "pairwise" fitting manner. We found that the simplified model containing logcx was superior to all alternative models. The most complicated individual regression was the most accurate, followed closely by the moderately complicated two-model global regression and then by the easy-to-perform onemodel global regression. The two-model global fitting was the most precise, followed by the individual fitting (closely) and by the one-model global fitting (from afar). Pairwise fitting (two E/c curves at once) improved the estimation. Thus, the two-model global fitting, performed pairwise, and the individual fitting are recommended for RRM, using the simplified model containing logcx. [ABSTRACT FROM AUTHOR]

The sensitive Fluorescence Assay by Gas Expansion (FAGE) method has been used to detect methyl peroxy (CH3O2) and hydroperoxyl (HO2) radicals after their conversion by titration with excess NO to methoxy (CH3O) and hydroxyl (OH) radicals, respectively, to study the kinetics of the reaction of CH3O2 + HO2 radicals. The rate coefficient of the reaction was measured in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) at 1000 mbar of synthetic air at T = 268–344 K, selectively detecting both radicals. Using a numerical model to fit both CH3O2 and HO2 radical temporal decays globally at each temperature investigated, rate coefficients for the reaction have been obtained. The room temperature rate coefficient was found to be kCH3O2 +HO2(295 K) = (4.6 ± 0.7) × 10−12 molecule−1 cm3 s−1 (2σ errors) and the temperature dependence of the rate coefficient can be characterized in Arrhenius form by kCH3O2 + HO2(268 K < T < 344 K) = (5.1 ± 2.1) × 10−13 × exp((637 ± 121)/T) cm3 molecule−1 s−1. The rate coefficients obtained here are 14%–16% lower than the literature recommended values with an uncertainty which is reduced significantly compared to previous reports. [ABSTRACT FROM AUTHOR]

The chaperone Hsp104, a member of the Hsp100/Clp family of translocases, prevents fibril formation of a variety of amyloidogenic peptides in a paradoxically substoichiometric manner. To understand the mechanism whereby Hsp104 inhibits fibril formation, we probed the interaction of Hsp104 with the Alzheimer's amyloid-ß42 (Aβ42) peptide using a variety of biophysical techniques. Hsp104 is highly effective at suppressing the formation of Thioflavin T (ThT) reactive mature fibrils that are readily observed by atomic force (AFM) and electron (EM) microscopies. Quantitative kinetic analysis and global fitting was performed on serially recorded 1H-15N correlation spectra to monitor the disappearance of Aβ42 monomers during the course of aggregation over a wide range of Hsp104 concentrations. Under the conditions employed (50 µM Aβ42 at 20 ℃), Aβ42 aggregation occurs by a branching mechanism: an irreversible on-pathway leading to mature fibrils that entails primary and secondary nucleation and saturating elongation; and a reversible off-pathway to form nonfibrillar oligomers, unreactive to ThT and too large to be observed directly by NMR, but too small to be visualized by AFM or EM. Hsp104 binds reversibly with nanomolar affinity to sparsely populated Aβ42 nuclei present in nanomolar concentrations, generated by primary and secondary nucleation, thereby completely inhibiting on-pathway fibril formation at substoichiometric ratios of Hsp104 to Aβ42 monomers. Tight binding to sparsely populated nuclei likely constitutes a general mechanism for substoichiometric inhibition of fibrillization by a variety of chaperones. Hsp104 also impacts off-pathway oligomerization but to a much smaller degree initially reducing and then increasing the rate of off-pathway oligomerization. [ABSTRACT FROM AUTHOR]

Abstract Background The initial step in comparing mathematical models to experimental data is to do a fit. This process can be complicated when either the mathematical models are not analytically solvable (e.g. because of nonlinear differential equations) or when the relation between data and models is complex (e.g. when some fitting parameters must be shared between many data sets). Results We introduce Simultant, a software package that allows complex fitting setups to be easily defined using a simple graphical user interface. Fitting functions can be defined directly as mathematical expressions or indirectly as the solution to specified ordinary differential equations. Analytical gradients of these functions, including the solution of differential equations, are automatically calculated to provide fast fitting even for functions with many parameters. The software enables easy definition of complex fitting setups in which parameters can be shared across both data sets and models to allow simultaneous fits to be performed. Conclusions Simultant exploits differentiable programming and simplifies modern fitting approaches in a unified graphical interface.

Background: The initial step in comparing mathematical models to experimental data is to do a fit. This process can be complicated when either the mathematical models are not analytically solvable (e.g. because of nonlinear differential equations) or when the relation between data and models is complex (e.g. when some fitting parameters must be shared between many data sets). Results: We introduce Simultant, a software package that allows complex fitting setups to be easily defined using a simple graphical user interface. Fitting functions can be defined directly as mathematical expressions or indirectly as the solution to specified ordinary differential equations. Analytical gradients of these functions, including the solution of differential equations, are automatically calculated to provide fast fitting even for functions with many parameters. The software enables easy definition of complex fitting setups in which parameters can be shared across both data sets and models to allow simultaneous fits to be performed. Conclusions: Simultant exploits differentiable programming and simplifies modern fitting approaches in a unified graphical interface. [ABSTRACT FROM AUTHOR]

Optimization of parameters and hyperparameters is a general process for any data analysis. Because not all models are mathematically well-behaved, stochastic optimization can be useful in many analyses by randomly choosing parameters in each optimization iteration. Many such algorithms have been reported and applied in chemistry data analysis, but the one reported here is interesting to check out, where a naïve algorithm searches each parameter sequentially and randomly in its bounds. Then it picks the best for the next iteration. Thus, one can ignore irrational solution of the model itself or its gradient in parameter space., Competing Interests: Disclosure statement The author declares no competing financial interest.

[Display omitted] • Particle swarm optimization automates global fitting of time resolved spectral data. • Particle swarm optimization eliminates manually setting initial parameters in conventional fitting. • Automation makes global analysis efficient and accessible for non-experts. Time-resolved spectroscopy, especially transient absorption spectroscopy (TAS), provides valuable insights to excited state dynamics. Analyzing TAS data involves fitting complex kinetic traces at various probe wavelengths using different rate equations. Conventional TAS global fitting methods require domain experts to establish physically valid models and provide good initial guesses to generate converged solutions. This poses challenges for non-experts who seek to utilize TAS, thus limiting its broader application and impact. To address this problem, we propose an intelligent optimization framework based on the particle swarm optimization (PSO) algorithm. In the proposed method, the PSO algorithm acts as the global fitting method to find the optimal values of the target variables or unknown parameters in the kinetics models. The target solution is optimized by iteratively updating candidate solutions with respect to an objective feedback signal. We demonstrated the effectiveness of the proposed PSO-based global fitting method with both synthetic and experimental datasets. The results show that our proposed method can successfully find the optimal target values in the global fitting process automatically, thus eliminating the iterative manual labor traditionally required. The proposed intelligent optimization framework provides a novel approach for automatic global fitting of TAS data, which significantly enhances the accessibility and utilization of the TAS methodology. [ABSTRACT FROM AUTHOR]

We report here the two-dimensional layered material of MoS 2 /Bi 2 Se 3 vdW heterostructures formed by ultrasonication of different concentrations of exfoliated MoS 2 and Bi 2 Se 3 nanosheets. The vdW heterostructures show unique optical characteristics compared to individual exfoliated nanosheets. The enhanced lifetime of heterostructures explained the charge transfer with increasing efficacy for producing optoelectronic devices. Raman spectroscopy confirms the presence of intrinsic Raman active modes of Bi 2 Se 3 , MoS 2 , and respective modes of vdW heterostructures. TEM images show characteristic lattice planes in both materials and clear overlapping regimes, confirming successful heterojunction formation. Further, Zeta potential confirms the enhanced stability of the heterostructures formed while the significant PL quenching, strongly suggests the presence of charge transfer processes within the heterostructures. Ultrafast pump-probe spectroscopy further confirms the non-linear charge transfer and relaxation mechanism of the heterostructures. We employed Surface Xplorer and Glotaran software for model fitting and Glotaran's global fitting revealed unresolved charge carrier dynamics. [ABSTRACT FROM AUTHOR]

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Graphical abstract Highlights • Sophisticated PELDOR/DEER data analysis software for Windows, macOS and Linux. • Global analysis of complex distance distributions. • Optimized data acquisition procedure saves measurement time. Abstract Pulsed electron–electron double resonance (PELDOR, alternatively called DEER for double electron–electron resonance) pulse sequences allow for the detection of echo decay curves that are modulated by dipole–dipole-coupling frequencies of interacting electron spins. With increasing distance between them, the echo decay needs to be monitored over a progressively extended time period. However, since the echo intensity typically falls off exponentially with increasing time, this might be problematic with respect to the minimum signal-to-noise ratio required for a sound data analysis. In this contribution we present the new PELDOR analysis tool GloPel (Glo bal analysis of PEL DOR data), an open-source Python-based application, that allows to extract improved-quality distance distributions from PELDOR data for which no ideal signal-to-noise ratio can be achieved for a very long observation window. By using Tikhonov regularization, GloPel allows for the simultaneous analysis of two time traces acquired for a sample in two different observation time windows, thus taking advantage of both, the typically high signal-to-noise ratio of the time trace acquired at early times of the echo decay, and the best possible background function fitted for the decay at later times, which is in most cases superimposed with considerable noise. In this way, short distances are not overseen in the higher noise of the longer time traces while long distances are not artificially shortened by limiting the observation time window of the experiment. Following our suggested data acquisition procedure, a significant reduction of the measurement time may also be achieved. [ABSTRACT FROM AUTHOR]

During translation, consecutive ribosomes load on an mRNA and form a polysome. The first ribosome binds to a single-stranded mRNA region and moves toward the start codon, unwinding potential mRNA structures on theway. In contrast, the following ribosomes can dock at the start codon only when the first ribosome has vacated the initiation site. Here we show that loading of the second ribosome on a natural 38-nt-long 5' untranslated region of lpp mRNA, which codes for the outer membrane lipoprotein from Escherichia coli, takes place before the leading ribosome has moved away fromthe start codon. The rapid formation of this standby complex depends on the presence of ribosomal proteins S1/S2 in the leading ribosome. The early recruitment of the second ribosome to the standby site before translation by the leading ribosome and the tight coupling between translation elongation by the first ribosome and the accommodation of the second ribosome can contribute to high translational efficiency of the lpp mRNA. [ABSTRACT FROM AUTHOR]

Mycobacterium tuberculosis MhuD catalyzes the oxygenation of heme to mycobilin; experimental data presented here elucidates the novel hydroxylation reaction catalyzed by this enzyme. Analogues for the critical ferric–hydroperoxoheme (MhuD–heme–OOH) intermediate of this enzyme were characterized using UV/Vis absorption (Abs), circular dichroism (CD), and magnetic CD (MCD) spectroscopies. In order to extract electronic transition energies from these spectroscopic data, a novel global fitting model was developed for analysis of UV/Vis Abs, CD, and MCD data. A variant of MhuD was prepared, N7S, which weakens the affinity of heme-bound enzyme for a hydroperoxo analogue, azide, without significantly altering the protein secondary structure. Global fitting of spectroscopic data acquired in this study revealed that the second-sphere N7S substitution perturbs the electronic structure of two analogues for MhuD–heme–OOH: azide-inhibited MhuD (MhuD–heme–N 3) and cyanide-inhibited MhuD (MhuD–heme–CN). The ground state electronic structures of MhuD–heme–N 3 and MhuD–heme–CN were assessed using variable-temperature, variable-field MCD. Altogether, these data strongly suggest that there is a hydrogen bond between the Asn7 side-chain and the terminal oxygen of the hydroperoxo ligand in MhuD–heme–OOH. As discussed herein, this finding supports a novel hydroxylation reaction mechanism where the Asn7 side-chain guides a transient hydroxyl radical derived from homolysis of the O O bond in MhuD–heme–OOH to the β- or δ- meso carbon of the porphyrin ligand yielding β- or δ-meso-hydroxyheme, respectively. Synopsis: In this work, it is shown that Mycobacterium tuberculosis MhuD utilizes a hydrogen bond between Asn7 and the terminal oxygen of a hydroperoxo ligand to orient hydroperoxo along the β/δ-axis of heme. This orientation promotes regiospecific hydroxylation of heme to β- and δ- meso -hydroxyheme. [Display omitted] • Asn7 forms a hydrogen bond with the terminal atom of the distal ligand to heme in MhuD. • The hydrogen bond between Asn7 and the distal ligand orients the ligand within the active site. • A hydrogen bond with Asn7 perturbs the electronic structures of analogues for the ferric–hydroperoxoheme intermediate. • Asn7 guides a transient hydroxyl radical to the β- and δ-meso carbons of heme. • A novel global fitting method was developed for the analysis of UV/Vis Abs, CD, and MCD data. [ABSTRACT FROM AUTHOR]

The Raman depolarization ratios of gaseous CO2 in the spectral range of 1240-1430 cm-1 are determined with a sensitive photoacoustic Raman spectroscopy, and more accurate data compared to the literature results are presented. The precision of the obtained depolarization ratio is achieved by measuring and fitting the dependence of the PARS signal intensity on the cross angle between the polarizations of two incident laser beams. [ABSTRACT FROM AUTHOR]

Abstract: l-DOPA-2,3-dioxygenase from Streptomyces lincolnensis is a single domain type I extradiol dioxygenase of the vicinal oxygen chelate superfamily and catalyzes the second step in the metabolism of the propylhygric acid moiety of the antibiotic, lincomycin. In this report, the kinetic mechanism of l-DOPA dioxygenase is interrogated using stopped-flow in order to determine microscopic rate constants. Pre-steady state, progress curve and steady-state data were combined in a global kinetic analysis using KinTek Explorer in order to define and constrain a kinetic model for the type I l-DOPA dioxygenase. The data are best described by a four step mechanism, in which the cyclization of the enzymatic product is not enzyme catalyzed. [Copyright &y& Elsevier]

[Display omitted] Dimethylarginine dimethylaminohydrolase (DDAH, EC 3.5.3.18) catalyzes the hydrolysis of asymmetric N ω, N ω-dimethyl- l -arginine (ADMA), an endogenous inhibitor of human nitric oxide synthases. The active-site cysteine residue has been proposed to serve as the catalytic nucleophile, forming an S -alkylthiourea reaction intermediate, and serving as a target for covalent inhibitors. Inhibition can lead to ADMA accumulation and downstream inhibition of nitric oxide production. Prior studies have provided experimental evidence for formation of this covalent adduct but have not characterized it kinetically. Here, rapid quench-flow is used with ADMA and the DDAH from Pseudomonas aeruginosa to determine the rate constants for formation (k 2 = 17 ± 2 s−1) and decay (k 3 = 1.5 ± 0.1 s−1) of the covalent S -alkylthiourea adduct. A minimal kinetic mechanism for DDAH is proposed that supports the kinetic competence of this species as a covalent reaction intermediate and assigns the rate-limiting step in substrate turnover as hydrolysis of this intermediate. This work helps elucidate the different reactivities of S -alkylthiourea intermediates found among the mechanistically diverse pentein superfamily of guanidine-modifying enzymes and provides information useful for inhibitor development. [ABSTRACT FROM AUTHOR]

Abstract: A critical assumption in using labeled antibodies is that the conjugation reaction has no deleterious effects on antibody avidity. This study demonstrates that this assumption need not hold true and presents a methodology to quantitatively determine the degree of inactivation and/or changes in antibody–antigen binding that can occur with conjugation. Fluorescein isothiocyanate (FITC) was conjugated to a mouse monoclonal antibody, Fc125, against hemagglutinin (HA) using varying fluorophore/protein (F:P) labeling ratios. Antibody binding, as a function of the F:P labeling ratio, was evaluated using a kinetic enzyme-linked immunosorbent assay (ELISA) and analyzed using global fitting. A two-parameter adjustment of the antibody concentration and the maximum rate was sufficient to describe the rate changes. The concentration parameter dominated the rate changes, consistent with the hypothesis that the coupling reaction inactivated an increasing fraction of the antibody population with a smaller change (∼15% at the highest F:P ratio) in antibody–antigen binding. An optimal F:P ratio that minimized both inactivation and unlabeled antibody was calculated. This procedure can be used to prepare functional, labeled antibody reagents with defined activity and can aid in quantitative applications where the stoichiometry and functionality of the labeled antibody are critical. [Copyright &y& Elsevier]

Abstract: We describe a new dynamic kinetic simulation program that allows multiple data sets to be fit simultaneously to a single model based on numerical integration of the rate equations describing the reaction mechanism. Unlike other programs that allow fitting based on numerical integration of rate equations, in the dynamic simulation rate constants, output factors, and starting concentrations of reactants can be scrolled while observing the change in the shape of the simulated reaction curves. Fast dynamic simulation facilitates the exploration of initial parameters that serve as the starting point for nonlinear regression in fitting data and facilitates exploration of the relationships between individual constants and observable reactions. The exploration of parameter space by dynamic simulation provides a powerful tool for learning kinetics and for evaluating the extent to which parameters are constrained by the data. This feature is critical to avoid overly complex models that are not supported by the data. [Copyright &y& Elsevier]

A femtosecond (fs) broad-band absorption apparatus was used to measure the early photoisomerization process of bacteriorhodopsin's (BR) photocycle to reveal the character of the important intermediate of J625 and to obtain a deeper understanding of the role of photoisomerization in BR photocycle. Two time constants of 0.5 PS (95%) and 2.0 ps (5%) were brought out by global fitting on thirty curves in the near-infrared region. We suggest that the first time constant results from the decay of I460 intermediate, and the longer component might be associated with BR isomer. The global analysis over 450, 540, 630,710 and 870 nm traces identified two time constants, ∼0.5 and ∼3 ps. The slower component can be extracted from the processes of both J625→BR568 (540 nm) and J625→K590 (630 nm), suggesting J-intermediate takes a partial cis configuration. The obvious negative feature in early delay time of 700-780 nm regions was attributed to the radiative transition (stimulated emission) from the Franck-Condon active configuration along the isomerization potential surface of all-trans-retinal. [ABSTRACT FROM AUTHOR]

Abstract: Neutron diffraction is a standard method for determining the structure of matter on an atomic scale; NMR cryoporometry is a recent widely applicable technique for characterising structure on a 2nm to scale. An extension of these techniques is described, Neutron Diffraction Cryoporometry (NDC). The information from a set of neutron diffraction measurements of liquids and their crystalline forms in meso-pores, as a function of temperature, is displayed as a cryoporometry graph. The data may then be conveniently interpreted using the Gibbs–Thomson relationship by analogy with the existing technique, NMR cryoporometry. Clear information is thus obtained on the relationship between phase and nano-structure, in a form well suited to further analysis. This method is applied to an equilibrium study of water/ice in SBA-15 templated silicas, as model nano- to meso-structured systems. The method described here uses global pattern matching (a one-dimensional morphing algorithm inside a linear least-squares fitting algorithm) applied to the full range of the diffraction data. This is a rapid method by comparison with the conventional method of fitting individual (overlapping) peaks, and has already led to NMR observations indicating plastic (rotator phase) ice in the same system. [Copyright &y& Elsevier]

Abstract: Fourier-transform far-infrared spectra of CH3 18OH in the 15–470cm−1 region have been analyzed by means of the Ritz assignment program. The far-infrared data have been combined with the literature microwave and millimeter-wave measurements in a full global fitting of the first three torsional states (ν t =0, 1, and 2) of the CH3 18OH ground vibrational state. The fitted dataset includes 550 microwave and millimeter-wave lines and more than 17000 Fourier-transform transitions covering the quantum number ranges J ⩽30, K ⩽15, and ν t ⩽2. With incorporation of 79 adjustable parameters, the global fit achieved convergence with an overall weighted standard deviation of 1.072, essentially to within the assigned measurement uncertainties of ±50kHz for almost all of the microwave and millimeter-wave lines and ±6MHz (0.0002cm−1) to ±15MHz (0.0005cm−1) for the Fourier-transform far-infrared measurements. Based on the global fit results, a database has been compiled containing transition frequencies, quantum numbers, lower state energies and transition strengths. This database will provide support for present and future astronomical studies, such as the on-going Orion surveys in preparation for the launch of the Herschel Space Observatory, in identifying isotopic methanol contributions to interstellar spectra. [Copyright &y& Elsevier]

L-type calcium-channel mutations causing hypokalemic periodic paralysis type 1 (HypoPP-1) have pronounced “loss-of-function” features and stabilize the less-selective second open state O2, as we demonstrated in the companion paper. Here, we compared the effects of the L-type calcium-channel activator (±)BayK 8644 (BayK) on the heterologously expressed wild-type (WT) calcium channel, rabbit Cav1.2 HypoPP-1 analogs, and two double mutants (R650H/R1362H, R650H/R1362G). Our goal was to elucidate (1) whether the “loss-of-function” in HypoPP-1 can be compensated by BayK application, (2) how the less-selective open state is affected by BayK in WT and HypoPP-1 mutants, as well as (3) to gain an insight into BayK mechanism of action. Ionic currents were examined by whole-cell patch-clamp and analyzed by the global-fitting procedure. Our results imply that (1) BayK promotes channel activation, but equalized the differences among the WT and mutants, thus attenuating HypoPP-related effects on activation and deactivation; (2) BayK binds to the first open state O1, and then serves as a catalyst for O2 formation; (3) binding of BayK is impaired in the HypoPP mutants, thus affecting the formation of the less-selective second open state; (4) BayK affects cooperativity between the single HypoPP-1 mutations at all stages of the channel gating; and (5) BayK favoring of O2 lowers calcium-channel selectivity. [ABSTRACT FROM AUTHOR]

Hypokalemic periodic paralysis type 1 (HypoPP-1) is a hereditary muscular disorder caused by point mutations in the gene encoding the voltage-gated Ca2+ channel α subunit (Cav1.1). Despite extensive research, the results on HypoPP-1 mutations are minor and controversial, as it is difficult to analyse Ca2+ channel activation macroscopically due to an existence of two open states. In this study, we heterologously expressed the wild-type and HypoPP-1 mutations introduced into the rabbit cardiac Ca2+ channel (R650H, R1362H, R1362G) in HEK-293 cells. To examine the cooperative effects of the mutations on channel gating, we expressed two double mutants (R650H/R1362H, R650H/R1362G). We performed whole-cell patch-clamp and, to obtain more information, applied a global fitting procedure whereby several current traces elicited by different potentials were simultaneously fit to the kinetic model containing four closed, two open and two inactivated states. We found that all HypoPP-1 mutations have “loss-of-function” features: D4/S4 mutations shift the equilibrium to the closed states, which results in reduced open probability, shorter openings and, therefore, in smaller currents, and the D2/S4 mutant slows the activation. In addition, HypoPP-1 histidine mutants favored the second open state O2 with a possibly lower channel selectivity. Cooperativity between the D2/S4 and D4/S4 HypoPP-1 mutations manifested in dominant effects of the D4/S4 mutations on kinetics of the double mutants, suggesting different roles of D2/S4 and D4/S4 voltage sensors in the gating of voltage-gated calcium channels. [ABSTRACT FROM AUTHOR]

Abstract: The parameters of the polyad models of the effective Hamiltonian of the 16O13C17O and 16O13C18O isotopologues of carbon dioxide have been refined by the least-squares fittings to the line positions collected from the literature. Such refinement has become necessary as the observed dataset has been significantly extended by our CW-CRDS observations in the 5900–7000cm−1 region. In the case of the 16O13C17O isotopologue, 1151 line positions of 11 bands have been used to refine the effective Hamiltonian parameters published by Chédin [A. Chédin, J. Mol. Spectrosc. 76 (1979) 430–491]. With the obtained set of parameters, the collected line positions are reproduced with a RMS (root mean squares of the residuals) equal to 0.0013cm−1. In the case of the 16O13C18O isotopologue, 61 parameters of the effective Hamiltonian were fitted to more than 6410 line positions. A weighted standard deviation of χ =1.77 and a global RMS of 0.0017cm−1, close to the experimental accuracy, were achieved. However, several rotational levels of the 31113 state (P =10) could not be reproduced in the frame of this polyad model and were then excluded from the fit. We found that these levels are affected by an anharmonic resonance interaction with the 51106 vibrational state (P =11) leading to energy shifts up to 0.060cm−1 and significant intensity transfer to several extra lines which could be detected. The coupling matrix element has been estimated to 0.11cm−1 from the detailed analysis of the experimental spectrum. This is the first evidence of an interpolyad resonance interaction in the case of the carbon dioxide molecule. In order to extend the input spectroscopic information, the weak lines left unassigned in our previous analysis of the CW-CRDS spectrum of the 13C enriched carbon dioxide [Y. Ding, P. Macko, D. Romanini, V.I. Perevalov, S.A. Tashkun, J.-L. Teffo, S.-M. Hu, A. Campargue, J. Mol. Spectrosc. 226 (2004) 146–160.] have been revisited. Thirteen 13C16O2 bands, one 16O13C17O band and two 16O13C18O bands could be newly assigned together with a number of transitions corresponding to high J values of previously observed bands. The spectroscopic constants G v, B v, and D v for the unperturbed bands have been fitted to the observed line positions. [Copyright &y& Elsevier]

Abstract: Tau protein, the major constituent of paired helical filaments in Alzheimer’s disease, belongs to the intrinsically disordered proteins (IDPs). IDPs are an emerging group in the protein kingdom characterized by the absence of a rigid three-dimensional structure. Disordered proteins usually acquire a “functional fold” upon binding to their interaction partner(s). This property of IDPs implies the need for innovative approaches to measure their binding affinity. We have mapped and measured the Alzheimer’s-disease-associated epitope on intrinsically disordered tau protein with a novel two-step sandwich competitive enzyme-linked immunosorbent assay (ELISA). This approach allowed us to determine the binding affinity of disordered tau protein in liquid phase without any disturbance to the competitive equilibrium and without any need for covalent or noncovalent modification of tau protein. Furthermore, the global fitting method, used for the reconstruction of tau binding curves, significantly improved the assay readout. The proposed novel competitive ELISA allowed us to determine the changes in the standard Gibbs energy of binding, thus enabling measurement of tau protein conformation in the core of paired helical filaments. IDP competitive ELISA results showed, for the first time, that the tau protein C terminus of the Alzheimer’s-disease-derived paired helical filaments core subunit adopts β-turn type I′ fold and is accessible from solution. [Copyright &y& Elsevier]

Photochemical reactions may involve complex reaction schemes and their investigation requires spectroscopic techniques extending over a broad spectral range and over several orders of magnitude in time. Two commonly used numerical procedures to evaluate such data sets – global fitting and singular value decomposition – are discussed and a method for the qualitative visualization is proposed: differentiation of the transient spectra on a logarithmic scale allows to extract special kinetic components and to obtain reasonable starting information for subsequent fitting procedures. The proposed method should be well adapted to situations where e.g. due to unstable samples the data cannot be recorded at the precision required for unambiguous analysis by standard data handling procedures. The method is applied to synthetic data sets as well as to experimental data taken from femtosecond absorption experiments on the laser dye DCM in DMSO. [Copyright &y& Elsevier]

A new approach is proposed to extract an object-level structured contour map from the junctions in a 2D image. Local junction structures are paired in order to initialize and globally constrain the contour extraction process. An original optimization method is applied to detect and describe the contours in respect of their inherent shape and structure. Any given contour is described using a proper number of constant-curvature primitives according to the complexity of its shape. The contour map produced is represented as a graph. The characterized contours correspond to the edges of the graph and their topological structure is described by the junctions at the vertices. An elaborated experimental evaluation illustrates the capabilities of the proposed approach in demanding situations. [Copyright &y& Elsevier]