Biomedical subjects

Dimitris Argyropoulos

Publications and source records attributed to Dimitris Argyropoulos.

5 recordsLinked to original sources

PubMed2006

Generic normalization method for real-time PCR. Application for the analysis of the mannanase gene expressed in germinating tomato seed.

A generic sample normalization method applicable in relative comparison of mRNAs quantified with real-time polymerase chain reaction (PCR) is proposed. The method was applied in samples obtained from tomato seeds after osmopriming and aging treatments and from untreated seeds at early imbibition stage, when seeds had not completed germination. Normalization in sample variations was accomplished by detecting synthetic DNA sequences tailing cDNA after second strand reverse transcription synthesis, while the use of the common normalizer GAPDH proved unreliable. Results, obtained from the new method and having a standard error less than 10%, verified the expression profile of a germination-specific mannanase gene that was closely recorded at different time intervals in relation to seed germination.

Gene Expression Regulation, Plant↗

PubMed2005

HPLC-NMR of fatty alcohol ethoxylates.

The application of HPLC-NMR for the analysis of a mixture of fatty alcohol ethoxylates (FAEs) is described. The use of the new generation, cryogenically cooled probes is investigated in respect of the sensitivity advantage that they provide. The FAE mixture is separated using liquid chromatography at the critical point of adsorption. The ability of the method to differentiate between the different end groups and the degree of polymerization of the mixture constituents is investigated. Both on-flow and stop-flow HPLC-NMR techniques were used together with two-dimensional NMR spectroscopy. The results are compared with those obtained by using an evaporative light scattering detector for the HPLC.

Chromatography, High Pressure Liquid↗

PubMed2005

Optimized mRNA isolation and assessment methodology with two-step real time PCR.

Messenger ribonucleic acid (mRNA) isolation from tomato seeds was performed with the PolyATtract System 1000 and was evaluated in two-step Real Time PCR using the fluoresence dye Sybr Green. The proposed isolation method resulted in cDNA production with Sybr Green 11-fold higher fluorescence intensity, having 87% lower standard deviation in the recorded fluorescence signals, and PCR efficiency improved by 21% in comparison to mRNA samples obtained with the manufacturer's protocol. The method for the assessment of the mRNA isolation procedure and the proposed mathematical analysis of the data are applicable to gene identification and expression studies for biotechnological applications.

DNA, Complementary↗

PubMed2002

Brasilane-type sesquiterpenoids from Laurencia obtusa.

[structure: see text] Three novel halogenated rearranged sesquiterpenes (1-3) have been isolated along with brasilenol (4) and epibrasilenol (5) from the organic extract of the red alga Laurencia obtusa, collected at Symi island in the Aegean Sea, Greece. The new metabolites possess the unusual skeleton of brasilane and contain the unprecedented 1,6-epoxy moiety. The structures of the new natural products, as well as their relative stereochemistry, were established by means of spectral data analyses, including two-dimensional NMR experiments along with molecular calculations.

Magnetic Resonance Spectroscopy↗

PubMed1996

Stereochemical Nonrigidity and Geometrical Isomerism in Six-Coordinate Trigonal Prismatic Complexes: The Case of Asymmetric Molybdenum and Tungsten Tris(dithiolenes).

The isomerization of nine asymmetric tris(dithiolenes) of tungsten and molybdenum, of the general formula (R(1)R(2)C(2)S(2))(3)M is studied with NMR methods. In the complexes investigated, R(1) = H, R(2) = p-CH(3)OPh, p-CH(3)Ph, or Ph, and M = W or Mo, or R(1) = H, R(2) = p-ClPh or p-BrPh, and M = W, or R(1) = Ph, R(2) = p-CH(3)OPh, and M = W, as shown in formula I. The complexes are proved to be trigonal prismatic in solution and stereochemically nonrigid at room temperature. An equilibrium favoring the trans isomer (formula III) is established, with the concentration of this isomer being three times that of the cis due to entropy reasons. The kinetics and mechanism of the isomerization is investigated and a scheme is proposed involving the rotation of only one ligand around an axis lying on the dithiolenic ring, passing from the metal to the center of the carbon-carbon bond. This mechanism satisfies energy criteria and is allowed by symmetry selection rules, as theoretical EHMO calculations indicate.

Journal Article↗