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At least 307 records · Page 17Linked to original sources
PubMed2006

Two-dimensional reverse phase-reverse phase chromatography: A simple and robust platform for sensitive quantitative analysis of peptides by LC/MS. Hardware design.

We have revised current two-dimensional RP-RP approaches and developed a new robust 2-D RP-RP platform. This platform was implemented on an Agilent 1100 2-D liquid chromatography system and is based on high pressure switching between two high-resolution RP columns. An independent binary gradient was implemented for each dimension. The powerful combination of dual analytical columns with independent gradient elution achieves high analyte purity, effectively eliminates matrix effects, and maximizes MS sensitivity in Q1 SIM comparable to the sensitivity enhancements of MS/MS-based methods. Implementation of dual simultaneous gradient profiles (overlapped gradients) reduces 2-D method run-time to the scale of 1-D method run-times. This robust and sensitive approach is particularly suitable for hydrophobic peptides and small proteins and can be used as a routine standard technique for enhanced on-line peptide purification coupled with mass spectrometric detection.

C-Peptide↗
PubMed1987

L-dopa causes an acute, partial and reversible reversal of denervation-induced supersensitivity of striatal dopaminergic receptors.

Denervation-induced supersensitivity of the striatal dopamine receptors can be quantified by the turning behaviour induced by apomorphine. With this experimental model we found that high-dose L-dopa/carbidopa administration reduced this supersensitivity. This effect was seen on the 1st day and did not alter over 5 or 10 days of treatment, but disappeared when medication was discontinued. The degree of reduction was the same, independent of the dose and period of administration. This effect could provide a useful model for studying the phenomenon of the irreversibility of the supersensitivity of the striatal dopamine receptors.

Animals↗
PubMed1985

On the reversibility of reversible MAO inhibitors.

The aim of this study was to assess a) the validity of an ex vivo approach for the estimation of the in vivo MAO A inhibitory properties of the new short-acting MAO A inhibitors, amiflamine, brofaremine, cimoxatone and moclobemide, by studying the effect of dilution of brain and liver homogenates from pretreated rats on the degree of enzyme inhibition; b) the displaceability of the inhibitors from the enzyme by substrate in brain and liver homogenates from pretreated rats; c) idem, in the in vivo situation in the brain, by increasing the availability of the substrate by releasing it from its endogenous stores by tetrabenazine. The following results were obtained: The ex vivo approach was found to be valid for moclobemide in brain and liver and for cimoxatone in brain tissue; a slight underestimation of the MAO A inhibitory effect of the latter in the liver is likely. Definite underestimation occurred with amiflamine in both tissues. Kinetic investigations using homogenates from pretreated rats showed amiflamine to be a competitive inhibitor; cimoxatone was competitive in the liver but showed a more complex pattern in the brain. Moclobemide was noncompetitive in both tissues, as has been shown previously for brofaremine. Moclobemide prevented the deamination of dopamine and serotonin released from their striatal stores by tetrabenazine nearly as efficiently as clorgyline at an otherwise equieffective dose; cimoxatone was somewhat less effective relative to the reference compound, as was brofaremine, which was however given at a more effective dose. Amiflamine was much less effective than clorgyline at protecting dopamine, but equieffective with respect to serotonin.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗