Macromolecular and elemental composition analysis and extracellular metabolite balances of Pichia pastoris growing at different oxygen levels.

Background: Analysis of the cell operation at the metabolic level requires collecting data of different types and to determine their confidence level. In addition, the acquired information has to be combined in order to obtain a consistent operational view. In the case of Pichia pastoris, information of its biomass composition at macromolecular and elemental level is scarce particularly when different environmental conditions, such as oxygen availability or, genetic backgrounds (e.

Metabolic flux profiling of Pichia pastoris grown on glycerol/methanol mixtures in chemostat cultures at low and high dilution rates.

The metabolic pathways associated with the tricarboxylic acid cycle intermediates of Pichia pastoris were studied using biosynthetically directed fractional 13C labelling. Cells were grown aerobically in a chemostat culture fed at two dilution rates (1.39x10(-5) s-1 and 4.

Measurement of the sign and the magnitude of heteronuclear coupling constants from spin-state-edited J-cross-polarization NMR experiments.

New spin-state-selective (S3) NMR pulse sequences exclusively applying cross-polarization schemes to achieve optimum homonuclear and heteronuclear 1H-X coherence transfer are reported for the simple and accurate measurement of the magnitude and sign of heteronuclear coupling constants for samples at natural abundance. The proposed spin-edited HCP-TOCSY experiments are based on clean heteronuclear S3 excitation, generated by simultaneous co-addition of two independent in-phase and anti-phase components created during the mixing heteronuclear J-cross-polarization (HCP) step, which is finally transferred to other protons by a conventional homonuclear TOCSY mechanism. Selective 1D and non-selective 2D approaches for the easy determination of long-range proton-carbon and proton-nitrogen coupling constants on any protonated and non-protonated heteronuclei are presented and discussed for several organic molecules.

Improved multiplicity-edited ADEQUATE experiments.

A very simple strategy is proposed to extract carbon multiplicity information along with the classic knowledge of carbon-carbon connectivities in ADEQUATE experiments without affecting the sensitivity ratios of the original pulse schemes. These new multiplicity-edited ADEQUATE experiments prove to be highly helpful for complete 1H and 13C resonance assignment and also for automated and easy spin system characterization of samples at natural abundance, using a single NMR experiment.

Preparation and structural study of the enantiomers of alpha,alpha'-bis(trifluoromethyl)-9,10-anthracenedimethanol and its perdeuterated isotopomer, highly effective chiral solvating agents.

Enantiopure forms of alpha,alpha'-bis(trifluoromethyl)-9,10-anthracenedimethanol and the corresponding perdeuterated isotopomers were prepared. The conformational study was carried out by (1)H NMR, and the absolute configuration was determined by the X-ray study of the crystallized diastereoisomeric carbamate derivative. This compound was tested as a chiral solvating agent (CSA).

The use of sample rotation for minimizing convection effects in self-diffusion NMR measurements.

Undesirable temperature gradients in a NMR sample tube are usually generated by an inappropriate temperature regulation system. We have shown that such convection effects can greatly distort the measurement of translational self-diffusion coefficients. The use of sample spinning helps to minimize such undesirable effects by disruption of convection fluxes due to resulting Coriolis forces that have a strongly stabilizing effect on the conducting state of the system (J.

Novel[1n]-meta-heterophane frameworks with a bis-betaine nature.

A convergent "5 + 1" and "5 + 3" synthetic strategy allowed the synthesis of the first examples of bis-betaines 2 and 3, a prototype of phanes that incorporate heterocyclic betaines. The structure of the quadrupolar macrocyclic systems 2 and 3 together with the dicationic [1(6)]- and [1(8)] meta-heterophane precursors 5*2X and 6*2X were examined by spectroscopy using 1H and 13C NMR techniques together with 1H-DNMR studies and electrospray ionization mass spectrometry.