IN VIVO CHLOROPHYLL a FLUORESCENCE TRANSIENTS AND THE CIRCADIAN RHYTHM OF PHOTOSYNTHESIS IN GONYAULAX POLYEDRA

Abstract— The intensity of chlorophyll a fluorescence during the early part of fluorescence induction at O , initial fluorescence, and P, peak fluorescence, was higher during the day phase of the circadian cycle than during the night phase in continuous light (LL) conditions and was positively correlated with the rate of oxygen evolution. The circadian rhythm in fluorescence in LL persisted in the presence of 10μM 3–(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), which blocks electron flow from photo-system (PS) II in photosynthesis. The rhythmic changes in fluorescence intensity are consistent with a lower rate constant for radiationless transitions during the day phase than during the night phase of the circadian rhythmicity. The circadian changes in the intensity of fluorescence were abolished at 77K, which may indicate the importance of structural changes in membranes in circadian oscillations.     

Screening and analytical confirmation of sulfonamide residues in milk by capillary electrophoresis-mass spectrometry

A new methodology is proposed to automate the monitoring of sulfonamide residues in milk samples. It combines a screening unit for the total amount of sulfonamide with capillary electrophoresis-mass spectrometry (CE-MS) equipment for processing the samples containing a detectable level of sulfonamide. The screening unit consists of continuous-flow system (CFS) to precipitate the proteins connected on-line to the CE-MS equipment, in which a common characteristic ion of all sulfonamides was monitored with the MS detector by flushing the sample through the capillary. The confirmatory method is based on the purification and preconcentration of sulfonamides in a CFS unit and posterior analysis by CE-MS. The sample treatment unit was also on-line connected to the CE-MS equipment. In order to increase sensitivity, the flow rate of the sheath liquid was diminished from 0.5 to 0.2 microL.min(-1) by increasing the content in water from 0 to 50% and the formic acid from 0.5 to 1.5% in this liquid and by applying an overimposed pressure of 5 mbar during the electrophoretic separation. The method allowed the analysis of 30 samples per hour.     

Method validation and qualification of instruments for atomic spectrometry

This work describes the analytical procedures for atomic absorption and inductively coupled plasma (ICP) techniques that have to be used in order to obtain a license to sell drugs in the USA. The qualification of atomic absorption spectrometers and ICP instruments is described. The method validation characteristics, e.g., accuracy, precision, linearity, range, detection limits, and quantification are discussed. The time involved and the quality of documentation are pointed out. The consequences for laboratory personnel and operating costs are also discussed.     

Synthesis and structure of a new rhodium(I) complex [Rh{P(OPh)3}3CN]

Summary The [Rh(acac){P(OPh)₃)}₂] complex (Hacac = 2,4-pentadione) reacts in solution with gaseous HCN in the presence of P(OPh)₃ to give [Rh{P(OPh)₃}₃CN]. Structural investigations of this complex including its³¹P n.m.r. spectra are reported.     

The surface of ordered mesoporous benzene-silica hybrid material: an infrared and ab initio molecular modeling study

Joint IR and computational results allow a detailed characterization of the surface properties of a mesoporous benzene-silica hybrid material with crystal-like wall structure. After outgassing at 450 degrees C, hydroxyl species mainly consist of noninteracting silanols, with both O-H and Si-O stretching modes at lower frequencies than those of SiOH in silica. Interaction with several probe molecules, followed both by experiment and calculus, shows that the aryl group in the coordination sphere of Si imparts a lesser acidity with respect to the isolated silanol in silica. In contrast, adsorption isotherms indicate that the interaction with acetone is stronger with benzene-silica than with silica: this is interpreted in terms of secondary interactions taking place between the slightly acidic CH in acetone and the electronic cloud in benzene-like rings. This suggests that both the inorganic component and the organic one play a role in dictating the surface behavior.     

Thin-Layer Chromatography with an Isolated Support and Forced Flow of the Mobile Phase

JPC – Journal of Planar Chromatography – Modern TLC -     

Molecular vibrations in a gradient extremal path

Summary The calculation of vibrational states using a gradient extremal path is discussed. Gradient extremal paths are defined by local criteria, which lead to stable solutions. This has certain advantages in comparison with a steepest-descent path, which is often difficult to determine accurately. For cases where a reaction path formalism is applicable, a path based on the gradient extremal concept gives results in close agreement with those obtained using traditional steepest-descent methods. We present algorithms for carrying out such calculations and also give some numerical results.     

Studies on the interaction between Se,Te, Cd,As and Zn and the distribution of Fe,Co, Rb and Hg in mice by instrumental neutron activation analysis

The incorporation of Se and Te into liver, kidneys, heart, spleen, lung and small intestine after i.p. injections of Balby mice with seleno-cystine (CySe)₂ and Na₂TeO₃ in the presence of Cd (as CdCl₂), As (as As₂O₃) and Zn (as ZnSO₄) has been studied. The change of contents of Co, Fe, Rb and Hg were determined in all investigated organs after injections with the above compounds. Instrumental neutron activation analysis was applied as the analytical method. It was found that a competitive interaction occurs between As and Se or Te. Similarly, this interaction has been observed between Se and Cd. The data obtained suggest that Cd has a higher competitive ability to displace Te than Zn and Se. Injection with the above compounds affects the contents of Fe, Co, Rb and Hg in all mice organs.     

Determination of dipole moment in the ground and excited state by experimental and theoretical methods of N-nonyl acridine orange

The absorption and fluorescence spectra of N-nonyl acridine orange are determined at room temperature (298 K) in cyclohexane, benzene, carbon tetrachloride, chloroform, chlorobenzene and dichloromethane. The ground state of dipole moment was obtained by impedance measurements using Guggenheim-Debeye's method. The experimental excited state dipole moment of N-nonyl acridine orange was determined using Bakhshiev's and Kawski-Chamma-Viallet's formulae and solvent polarity parameter proposed by Reichardt. These experimental results were completed with theoretical results using quantum chemical methods. The experimental (muexp=10.76 D) and theoretical (mucal=9.9 D) dipole moments in the ground and excited state (muexp*=14.56 D) were compared.     

Generalized inverse method for computation of molecular force field

The generalized inverse method is applied to the force constants calculation problem having a nearly singular Jacobian matrix, and by substituting it by one of lower rank which is near to it and well conditioned it is possible to eliminate the convergence difficulties of the least squares iteration process. A further significant advantage of the method is that certain matrix theoretical considerations give the possibility of deciding at the end of the iteration which force constants are determined by the available observations. Numerical results for the dimethylmercury molecule are given.