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Biomedical subjects

M Palumbo

Publications and source records attributed to M Palumbo.

At least 163 records · Page 9Linked to original sources
PubMedDate not supplied

On the oxy analogues to the 3 leads to 1 intramolecularly hydrogen-bonded peptide conformations.

The possible occurrence of the oxy analogues to the 3 leads to 1 intramolecularly hydrogen-bonded peptide conformations (main feature of the gamma turn), recently proposed in solution by several authors, has been investigated in a number of N-tert-butyloxycarbonyl-alpha-amino acids by x-ray diffraction, infrared absorption, proton magnetic resonance, and circular dichroism techniques. These folded conformations are absent in the solid state in all cases so far examined; however, they seem to be present in solution, the extent of the population of these forms in the conformational equilibrium mixtures being solvent, temperature, and structure dependent. In the solid state N-tert-butyloxycarbonyl-D-valine has the urethane-CONH-group in the cis configuration; this is the first time such a configuration has been found in the solid-state for a secondary amide group in a linear compound.

Binding Sites↗
PubMedDate not supplied

Metal complexes of poly(alpha-amino acids). A potentiometric and circular dichroism investigation of Cu(II) complexes of poly(L-lysine), poly(L-ornithine), and poly(L-diaminobutyric acid).

The conformational properties of cupric complexes of poly(L-lysine), poly(L-ornithine), and poly(L-diaminobutyric acid) have been investigated by potentiometric, visible and UV absorption, and circular dichroism (CD) techniques. The three polymers form two kinds of complexes stable at pH less than 8.5 (type I complexes) and at pH less than 8.5 (type II complexes). It has been found that in the low pH complexes of poly(L-diaminobutyric acid) at least one deprotonated amido nitrogen is coordinated to cupric ions. Type II complexes involve always amide nitrogens in the coordination sphere of Cu(II). Evidence is presented that the structure of such complexes is not compatible with the alpha-helical conformation of the peptide backbone.

Aminobutyrates↗
PubMedDate not supplied

Solid-state and solution conformation of N-tert-butyloxycarbonyl-L-prolylglycine.

The occurrence of the oxy analogue in the trans-II 4 leads to 1 intramolecularly hydrogen-bonded nonhelical peptide conformation, recently proposed for t-BOC-L-Pro-Gly-OH in the solid state on the basis of infrared absorption evidence, has been disproved by x-ray diffraction analysis. This type of folding is also absent in polar solvents. However, in solvents of low polarity the presence of this folded form cannot be excluded.

Circular Dichroism↗
PubMedDate not supplied

[Conservative surgery in the treatment of rectal tumors. Our experience, 1986-1997].

OBJECTIVE: Our institution's experience with low anterior resection for primary rectal cancer was reviewed to determine cancer treatment results and to identify risk factors for pelvic recurrence. METHODS: Ninety-two patients treated for primary rectal cancer between 1986 and 1997 were studied retrospectively. All cases was classified according to Astler-Coller. Median follow up was 46 months. RESULTS: Actuarial 5-year survival for all patients was 79%. Among 28 patients who relapsed, only 9 pelvic recurrence was detected with an actuarial rate of 15% at 5 years. Lymph nodes involvement were associated with increased risk for pelvic recurrence. DISCUSSION: Low anterior resection permitted by circular stapler provides good treatment for mid-rectal cancers and for some distal rectal cancers. Pelvic recurrence is not correlated with neoplasm localization, T stage and short distal resection margins, but only with the presence of lymph nodes involvement. This result increase the value of the hypothesis that search the pelvic recurrence origin in a extra-parietal disease respect anastomotic disease. CONCLUSION: Fundamental to prevent pelvic recurrence is the surgical technique that have to remove lymph node en bloc with the rectum doing a dissection along the endopelvic fascia to Denonvillers fascia so to take away completely the mesorectum.

Adenocarcinoma↗
PubMedDate not supplied

Case study. Fractured ankle.

To improve our practice performance for patients admitted to the emergency department with fractured ankles, our Clinical Quality Improvement Team (CQI) developed the Fractured Ankle Critical Path, for patients needing open reduction and internal fixation, but for whom surgery could or should be deferred as determined by the orthopaedic surgeon. Members of the team included an orthopaedic trauma surgeon, an emergency department physician, case managers, and representatives of the Home Care Department at Rhode Island Hospital. The critical path includes a Home Care referral procedure, an R.I. Hospital Fracture and Orthopaedic Information Sheet, and a Fractured Ankle Home Care Protocol. The goal of the Fractured Ankle Critical Path is to decrease length of stay while maintaining positive outcomes.

Adult↗
PubMedDate not supplied

[Molecular construction (superstructures) with adjustable properties based on double-stranded nucleic acids].

Formation of molecular construction that consists of double-stranded molecules of nucleic acids (or synthetic polynucleotides) located at the distance 30-50 A in the spatial structure of particles of their cholesteric liquidcrystalline dispersion and crosslinked by polymeric chelate bridges is described. The resulting superstructure, which possesses peculiar physicochemical properties, could be used as integral biosensor whose properties depend on temperature, the presence of chemical or biologically active compounds of different nature, etc.

Antibiotics, Antineoplastic↗
PubMedDate not supplied

[Enzymatic cleavage of superhelical DNA in a liquid crystal state].

Superhelical pBR322 DNA molecules form liquid-crystalline dispersions in water-salt solutions containing poly(ethyleneglycol). The formation of the liquid-crystalline dispersions from superhelical DNA molecules results in the appearance of two sites inside the DNA molecules that are split by Micrococcal nuclease. The first site of digestion does not differ from the standard site split by this enzyme in water-salt solutions, whereas the second one represents a new site specific only for the DNA molecules forming liquid-crystalline dispersions. Splitting of the DNA molecule through the first site is accompanied by formation of its linear form; splitting of a new site results in the formation of two linear DNA fragments with molecular masses equal to half of the initial DNA molecules. Enzyme digestion of superhelical DNA molecules forming liquid-crystalline dispersions induces a reformation of the "nonspecific" space organization of dispersions to the cholesteric one. A hypothetic model for packing of the superhelical DNA molecules inside liquid-crystalline dispersions and its transformation under enzyme action is suggested.

Circular Dichroism↗
PubMedDate not supplied

[Principles of creating biotransducers based on nucleic acid liquid crystals].

A brief concept of biosensors is presented. Structural peculiarities and properties of single- and double-stranded nucleic acids that are to be taken into account when creating sensing units for biosensors using different principles of molecular recognition are considered. General schemes of sensing units based on liquid-crystalline dispersions formed from low-molecular mass DNA, its complexes with "cross-linking" agents and from circular superhelical DNA molecules are described.

Base Sequence↗
PubMedDate not supplied

[Nucleic acids as a basis for creating biosensors].

Here we present a brief conception of biosensors. Structural peculiarities and properties of single- and double-stranded nucleic acids that are to be taken into account when creating biosensors on the basis of these biomolecules are considered. On the example of two biologically active compounds a possibility is shown for constructing biosensors on the basis of liquid-crystalline dispersions of low molecular mass DNA and on the basis of liquid-crystalline DNA dispersions immobilized due to their inclusion into the synthetic polymeric matrix.

Biosensing Techniques↗
PubMedDate not supplied

[Anomalous optical activity induced during condensation of various spatial forms of double-stranded circular DNA].

Formation of dispersed phases from complexes of (closed circular DNA (c.c. DNA)--antibiotics (drugs) in PEG-containing solutions has been studied. It is shown that under definite concentrations of bound antibiotics relatively intense bands in the CD spectra of dispersed phases in the absorption region of DNA and antibiotics chromophores appear. The properties of liquid crystalline phases formed from the complexes of linear DNA with antibiotics were compared to those of dispersed phases formed from c. c. DNA. Such comparison demonstrates existence of some differences in the optical properties of the phases formed from linear and c.c. DNA molecules. For example a change of the bands sign in the CD spectra of dispersed phases formed from the complexes (c.c. DNA--antibiotics), which is the case with all the substances studied, does not exist in the case of liquid crystalline phases formed from the complexes of (linear DNA--antibiotics). It was shown that a change of the bands sign in the CD spectra correlates with a change of the sign of superhelical twist of closed circular DNA molecules.

Antibiotics, Antineoplastic↗
PubMedDate not supplied

["External chromophores" and intensive bands in circular dichroism spectra of liquid-crystalline microphases of nucleic acids].

From the analysis of CD-spectra of liquid crystalline microphases formed from DNA molecules in complexes with "external chromophores" requirements are formulated for the compounds to be used in revealing peculiarities of spatial structure of nucleic acids liquid crystalline microphases. These requirements satisfied it is possible to record the CD-spectra having intensive bands in the regions of chromophores absorption. These bands prove the helical pattern of the spatial structure of nucleic acid liquid crystalline microphase.

Chemical Phenomena↗