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M Matzeu

Publications and source records attributed to M Matzeu.

At least 19 recordsLinked to original sources
PubMed2001

Torsional constant of 27-mer DNA oligomers of different sequences.

We have studied the torsional elastic constant (alpha) of short DNA (27mer) oligomers of various sequence by fluorescence polarization anysotropy (FPA) measurements. The lowest alpha values were found in samples with sequence rich in AA dinucleotides or containing the alternating d(A-T) x d(A-T) motif. The torsional rigidity of our DNA samples was compared to that calculated according to the current values of twist angle fluctuations derived for ten dinucleotide steps by recent analyses of DNA crystal structure database. The values of torsional rigidity derived from crystals are higher than our experimental ones, obtained by FPA analysis, suggesting that packing force in crystals may notably hinder the dinucleotide twist angle fluctuations that occur in solution. This behaviour is more evident for samples containing AA, TA and AT steps. In all the samples there is about a twofold change of the alpha value in the 10-40 degrees C range. An activation enthalpy (Delta H (#)) of about 17.4 kJ mol(-1), on average, was obtained for the temperature dependence of eight of the ten samples studied. A correlation with the stacking energy is discussed.

Base Sequence↗
PubMed2000

DNA, RNA and hybrid RNA-DNA oligomers of identical sequence: structural and dynamic differences.

A 27-mer sequence was synthesised as DNA duplex (DD), RNA duplex (RR), and RNA-DNA (RD) hybrid in order to characterise their structural and dynamic features. The hydrodynamic radius (Rh) and the rise (b) values of the three samples were consistent with the conformations predicted by CD analysis. The value of the torsional constant (alpha) of the samples containing RNA was approximately twice that of the DD sample and followed the order: DD < RD < RR. The same order was observed in the thermodynamic stability and in the reduction of the electrophoretic mobility. gamma-Ray footprinting analysis was carried out to resolve the individual strand conformation in the hybrid. The RNA strand preserved its conformation, while the DNA strand showed local deformations mainly at TA and TG steps.

Algorithms↗
PubMed2000

gamma-Ray footprinting and fluorescence polarization anisotropy of a 30-mer synthetic DNA fragment with one 2'-deoxy-7-hydro-8- oxoguanosine lesion.

The influence of the oxidative lesion 2'-deoxy-7-hydro-8-oxoguanosine (8-oxodG) on some conformational properties of DNA has been studied. Four 30-mer duplexes of the form [5'-GATCCTCTAGAGTC[G(*) or G]ACCTGCAGGCATGCA-3']:[3'-CTAGGAGATCTCAG[C or A]TGGACGTCCGTACGT-5'], in which G(*) is the 8-oxodG lesion, were synthesized in order to compare the effect of the GA mismatch and of the damaged G(*)C and G(*)A forms with the normal GC. Spectroscopic measurements performed by means of UV denaturation and circular dichroism experiments do not show gross changes of stability and overall structure in the damaged and mismatched samples. The control DNA and the samples containing GA mismatch show very similar gamma-rays cutting patterns, indicating that the introduction of the GA mismatch does not perturb the phosphate backbone geometry. In the samples containing the 8-oxodG there are some variations of the cleavage pattern near G(*) which are extended for almost one helical turn. Some differences are observed between G(*)C and G(*)A duplexes. In particular, in the G(*)C sample the reduced accessibility to OH radicals at the G15 site, observed in the control, spreads on the intrastrand adjacent bases and in the G(*)A sample a shift of the minimum is observed. The hydrodynamic radius R(h) derived by fluorescence polarization anisotropy decay exhibits a constant value of 11.4 +/- 0.2 A between 5 and 40 degrees C, in all the samples. The torsional constant alpha of each oligomer decreases when the temperature is raised and the alpha values of the damaged samples are higher than those of the normal ones.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

Radiation damage to triplex DNA induced by gamma-rays: a footprinting study and Monte Carlo simulation.

PURPOSE: This study is aimed at comparing the radiosensitivity of a 21-mer DNA fragment in duplex and triplex form (Py x Pu duplex and Py x Pu:Py triplex) and to give insights into the fine structural features due to the different strandedness. MATERIALS AND METHODS: The triplex sample was characterized by means of electrophoretic mobility, circular dichroism spectra and UV melting experiments. Triplex and duplex, labelled on the homopyrimidine or homopurine strand, were irradiated with 60Co gamma-rays. The samples were analysed by sequencing gel electrophoresis and the patterns of relative probabilities of frank strand breakage (FSB) and alkali-revealed breakage (ARB) at each nucleotide site were determined. Relative probabilities of OH* radical attack to duplex and triplex DNA built up with a molecular modelling software were calculated using a previously reported simulation procedure (Sy et al. 1997). The experimental data were compared with the results of the theoretical simulations of OH* radical attack to DNA. RESULTS: Globally, the duplex is more attacked than the triplex, mainly in the Pu strand. Sequence-dependent variations of FSB and FSB+ARB probabilities in both duplex and triplex were revealed. No significant differences between the patterns of damage in the triplex and in the duplex were observed. CONCLUSIONS: The presence of the third Py strand located in the major groove of the DNA duplex modifies the total yields of radiation-induced DNA damage, but not the sequence-dependent patterns of relative probability of damage at each nucleotide site.

Base Sequence↗
PubMed1999

Structural and dynamical properties of two DNA oligomers with the same base composition and different sequence.

We compared the structural and dynamical properties of two DNA fragments, 27 bp long, having the same base composition but a different sequence. This work aims to understand how the base sequence on a purine rich strand in a double helix, which is important for many biological functions, is related to structural features and to measurable physical quantities. Structural characterization of the two samples was performed both by conventional spectroscopic methods (circular dichroism and UV denaturation experiments) and by means of a gamma-ray footprinting technique which gives information on fine conformational differences. Dynamical features of the samples were studied by fluorescence polarization anisotropy (FPA) measurements which allow the evaluation of some hydrodynamic parameters, such as the hydrodynamic radius and the elastic torsion constant of DNA. Using a gamma-ray footprinting technique, we observed that the interruption of the long homopurine-homopyrimidine run in the control sample, due to the 'scrambling' operation, alters the DNA three-dimensional structure, also at nucleotide level. Besides, an increase in thermal stability and in the torsional rigidity of the 'scrambled' sample was observed. A possible association between base-stacking interaction and torsional rigidity was inferred from the comparison of the two samples.

Algorithms↗
PubMed1998

Triple helix DNA oligomer melting measured by fluorescence polarization anisotropy.

A synthetic DNA triple helix sequence was formed by annealing a pyrimidinic 21 mer single strand sequence onto the complementary purinic sequence centred on a 27 mer duplex DNA. Melting of the third strand was monitored by UV spectrophotometry in the temperature range 10-90 degrees C. The T(m) of the triplex, 37 degrees C, was well separated from the onset of duplex melting. When the same triple helix was formed on the duplex bearing one nick in the center of the pyrimidinic sequence the T(m) of the triplex was shifted to approximately 32 degrees C and overlapped the melting of the duplex. We have used fluorescence polarization anisotropy (FPA) measurements of ethidium bromide (EB) intercalated in duplex and triplex samples to determine the hydrodynamic parameters in the temperature range 10-40 degrees C. The fluorescence lifetime of EB in the samples of double and triple stranded DNA is the same (21.3 +/- 0.5 ns) at 20 degrees C, indicating that the geometries of the intercalation sites are similar. The values for the hydration radii of the duplex, normal triplex, and nicked triplex samples were 10.7 +/- 0.2, 12.2 +/- 0.2, and 12.0 +/- 0.2 A. FPA measurements on normal triplex DNA as a function of temperature gave a melting profile very similar to that derived by UV absorption spectroscopy. For the triplex carrying a nick, the melting curve obtained using FPA showed a clear shift compared with that obtained for the normal triplex sample. The torsional rigidity of the triplex forms was found to be higher than that of the duplex form.

Base Sequence↗
PubMed1993

Influence of defects on the electrophoretic, thermodynamic and dielectric properties of a 21 base pair DNA in solution.

The thermodynamic and dielectric properties of a 21 base pair DNA have been evaluated and compared with those of samples with some defects. In particular, fragments in which the absence of a phosphate group (nick) or of two nucleotides (gap) causes chain interruptions were studied. Measurements of ultraviolet absorption as a function of temperature at different oligomer concentrations and at various ionic strengths were performed. Dielectric spectroscopy at radiofrequencies (1 MHz-1 GHz) was applied on aqueous solutions of the duplexes at 5 degrees C, where the solutes are thermally stable. Dielectric dispersions with 30-40 MHz characteristic frequencies were defined. The results of melting experiments indicate a thermal destabilization of the oligomers containing the defects. Electrophoretic data and the dielectric results show that the conformations of the nicked and control samples are very similar, while the oligomer with a gap is more compact with a different charge distribution at the ends.

Base Composition↗
PubMed1990

[The use of endobronchial aztreonam in the treatment of bronchiectatic suppuration].

The authors submitted 8 patients with bronchiectasis to endobronchial therapy with Aztreonam 2 gr twice a week for 4 weeks after endobronchial lavage with sodium chloride solution. They observed a definite clinical and radiological improvement and a stabilized condition of the disease was observed. No hepatic or renal toxicity was detected.

Adult↗
PubMed1988

Measurement of ultraviolet radiation emitted from welding arcs.

It is well known that exposure to UV radiation can result in short- and long-term injury to the eyes and skin. Exposure to UV radiation is generally associated with many production processes involving either the use of UV or the emission of unwanted UV as a by-product. Welding arc machines are widespread sources of intense UV, as well as visible and infrared radiation. To evaluate the hazard associated with UV exposure during welding processes, the spectral irradiance must be measured and weighted in terms of biological effectiveness. Standardization of routine field measurement procedures is difficult because the emission depends on time dependent parameters. This paper presents a procedure suitable for the spectral irradiance measurement of welding arcs in the 250-400 nm range as well as other unstable sources.

Environmental Exposure↗
PubMed1982

Irradiance measurements of some UV sources.

The use of UV radiation sources in the scientific, medical and industrial fields is becoming increasingly widespread. This poses the problem of protection and calls for a set of rules fixing the maximum exposure values for the organs subjected to the radiation hazard. The purpose of this work is to analyze some commonly used sources by first determining the spectral composition of the radiation emitted in the 200-400 nm range, and the total effective irradiance from which the maximum exposure time is inferred. The latter is measured on the basis of the criteria fixed by ACGIH. The final interests is that of providing some evaluation of the hazards connected with the use of some widely used sources.

Disinfection↗
PubMed1980

[Levamisole in lung diseases].

Several years of experience have demonstrated that levamisole can be used on a wide scale in pneumology, not only in lung cancer but also in: chronic and acute tuberculosis, in purulent bronchiectasic bronchitis, in lung abscess, in sarcoidosis and in some lung mycosis. In fact, in our patients we have observed a marked improvement of the clinical and radiological conditions and of the immunological data. In several cases the satisfactory results obtained remained unchanged during the whole period of our control (8 months): in other cases showing the beginning of an impairment a new short period of treatment with levamisole following the usual schedule was sufficient to block the threat of a worsening situation.

Humans↗
PubMed1975

[Use of 48/80 in the diagnosis and therapy of allergic asthma].

A review of the relevant literature is followed by the presentation of experimental and clinical results obtained with intradermal administration of the histamine releaser 48/80. The value of this substance in the diagnosis and treatment of bronchial asthma is stressed.

Asthma↗