6,7-Dimethyl-5-phenyl-1H-thieno[2,3-e]-[1,4]diazepin-2(3H)-one

In the title molecule, C15H14N2OS, the seven-membered ring adopts a boat conformation. The carbonyl, imine and phenyl groups lie to one side of the molecule, and the thienyl ring and methylene group to the other.

Carbohydrate-electrolyte feedings and 1h time trial cycling performance

The effects of a commercial sports drink on performance in high-intensity cycling was investigated. Nine well-trained subjects were asked to complete a set amount of work as fast as possible (time trial) following 24 h of dietary (subjects were provided with food, energy 57.4 ± 2.4 kcal/kg and carbohydrate 9.1 ± 0.4 g/kg) and exercise control. During exercise, subjects were provided with 14 mL/kg of either 6% carbohydrate-electrolyte (CHO-E) solution or carbohydrate-free placebo (P).

Probing the flexibility of the DsbA oxidoreductase from Vibrio cholerae - a 15N -1H heteronuclear NMR relaxation analysis of oxidised and reduced forms of DsbA

We have determined the structure of the reduced form of the DsbA oxidoreductase from Vibrio cholerae. The reduced structure shows a high level of similarity to the crystal structure of the oxidized form and is typical of this class of enzyme containing a thioredoxin domain with an inserted α-helical domain. Proteolytic and thermal stability measurements show that the reduced form of DsbA is considerably more stable than the oxidized form. NMR relaxation data have been collected and analyzed using a model-free approach to probe the dynamics of the reduced and oxidized states of DsbA. Akaike's information criteria have been applied both in the selection of the model-free models and the diffusion tensors that describe the global motions of each redox form. Analysis of the dynamics reveals that the oxidized protein shows increased disorder on the pico- to nanosecond and micro- to millisecond timescale. Many significant changes in dynamics are located either close to the active site or at the insertion points between the domains. In addition, analysis of the diffusion data shows there is a clear difference in the degree of interdomain movement between oxidized and reduced DsbA with the oxidized form being the more rigid. Principal components analysis has been employed to indicate possible concerted movements in the DsbA structure, which suggests that the modeled interdomain motions affect the catalytic cleft of the enzyme. Taken together, these data provide compelling evidence of a role for dynamics in the catalytic cycle of DsbA.

(±)-1-Hydr­oxy-6,6-dimethyl-1H,6H-naphtho[1,2-c]furan-3,9-trione

The title compound, C₁₄H₁₂O₄, crystallizes as discrete mol­ecular species which form hydr­oxy-to-ketone hydrogen-bonded dimers disposed about crystallographic centres of symmetry.

Why is it so? The 1H-NMR CH2 splitting in substituted propanes

Nuclear magnetic resonance (NMR) spectroscopy is an important tool in the structural analysis of both organic and inorganic molecules. Proton NMR spectra can yield information about the chemical or bonding environment surrounding various protons, the number of protons in those environments, and the number of neighbouring protons around each proton. However, there is a common misconception about the relationship between the splitting of signals due to the neighbouring protons and the (n+1) rule. This paper discusses how the appearance of deceptively simple spectra has led to this misconception and the correct interpretation and application of the (n+1) rule.

An inclusion complex of β-Cyclodextrin-L-Phenylalanine : 1H NMR and molecular docking studies

An inclusion host-guest complex between β-cyclodextrin (β-CD) and L-phenylalanine (LPhe) was investigated using ¹H nuclear magnetic resonance spectroscopy and molecular docking techniques. ¹H chemical shift changes of β-CD were used to calculate the stability constant (K_stb) of the complex. On the basis of the Hildebrand-Benesi method, the K_stb of the 1:1 complex in D₂O solution at 300 K, pD 7.6 was of 25.5 M^-1, implying a fast intermolecular exchange rate process. Interestingly, docking simulation indicates the toroidal space can be occupied by L-Phe with two favorable arrangements. For the predicted model with the higher probability score, the L-Phe aromatic ring is facing to the secondary hydroxyl groups of β-CD. Results from NMR and docking simulation are in good agreement with the x-ray structures of β-CD/L-phenylalanine derivatives.

Determining binding constants from 1H NMR titration data using global and local methods : a case study using [n]polynorbornane-based anion hosts

From data generated using 1H NMR titrations, different methodologies to calculate binding constants are compared. The ‘local’ analysis method that uses only a single isotherm (only one H-bond donor) is compared against the ‘global’ method (that includes many or all H-bond donors). The results indicate that for simple systems both methods are suitable, however, the global approach consistently provides a K a value with uncertainties up to 30% smaller. For more complex binding, the global analysis method gives much more robust results than the local methods. This study also highlights the need to explore several different modes when data do not fit well to a simple 1:1 complexation model and illustrates the need for better methods to estimate uncertainties in supramolecular binding experiments.

1H-NMR and mass spectrometric characterization of the metabolic response of juvenile Atlantic salmon (Salmo salar) to long-term handling stress

Stressors of various kinds constantly affect fish both in the wild and in culture, examples being acute water temperature and quality changes, predation, handling, and confinement. Known physiological responses of fish to stress such as increases in plasma cortisol and glucose levels, are considered to be adaptive, allowing the animal to cope in the short term. Prolonged exposure to stressors however, has the potential to affect growth, immune function, and survival. Nonetheless, little is known about the mechanisms underlying the long-term stress response. We have investigated the metabolic response of juvenile Atlantic salmon (Salmo salar) to long-term handling stress by analyzing fish plasma via ¹H nuclear magnetic resonance spectroscopy and ultra high performance liquid chromatography–mass spectrometry (UPLC–MS), and comparing results with controls. Analysis of NMR data indicated a difference in the metabolic profiles of control and stressed fish after 1 week of stress with a maximum difference observed after 2 weeks. These differences were associated with stress-induced increases in phosphatidyl choline, lactate, carbohydrates, alanine, valine and trimethylamine-N-oxide, and decreases in low density lipoprotein, very low density lipoprotein, and lipid. UPLC-MS data showed differences at week 2, associated with another set of compounds, tentatively identified on the basis of their mass/charge. Overall the results provided a multi-faceted view of the response of fish to long-term handling stress, indicating that the metabolic disparity between the control and stress groups increased to week 2, but declined by weeks 3 and 4, and revealed several new molecular indicators of long-term stress.