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H Neubacher

Publications and source records attributed to H Neubacher.

13 recordsLinked to original sources
PubMed2006

Spectrometric measurement in laryngeal cancer.

Only early diagnosis of laryngeal cancer can prevent major or mutilating treatment. Recently, autofluorescence endoscopy has been developed to enhance endoscopic information and succeeded in facilitating the detection and demarcation of precancerous lesions, carcinoma in situ and cancer of the larynx. The aim of the present study is to quantify autofluorescence imaging by spectroscopy in order to validate the above mentioned findings. In a prospective study, 42 patients with suspected one-sided precancerous or cancerous lesions of the vocal folds were investigated during microlaryngoscopy. Autofluorescence (AF) was induced by filtered blue light (375-440 nm) of a xenon short arc lamp and processed by a CCD camera system (D-light AF System, STORZ, Germany). Autofluorescence images were gathered in a contact mode. For spectrometric measurements an optical multi channel analyzer (AVS-USB 2000, Avantes, The Netherlands) was applied. The results were compared to pathohistological findings. Under blue light excitation normal mucosa presented a bright green fluorescence. Intensity increased from the ventricular folds to the subglottic area. Averaged spectra of the normal laryngeal mucosa demonstrated different fluorescence maxima at 475, 515, 550, 600 and 630 nm. Highest intensity was measured at 515 nm explaining the green appearance of the autofluorescence picture. In contrast, precancerous as well as cancerous lesions showed a significant decrease in autofluorescence intensity with a reddish-violet color. Highest loss of autofluorescence intensity was measured at 515 nm. At this wave length intensity dropped 70% on average in comparison to the regularly appearing contralateral vocal fold. In contrast to 515 nm, the loss of intensity at 630 nm amounted to 38%. Sensitivity amounted to 97% and specificity to 82%. Comparable to autofluorescence endoscopy a differentiation between precancerous and cancerous lesions could not be detected. The reason for the loss of autofluorescence may predominantly be caused by mucosal thickening but also by changes in metabolism and higher nuclei density.

Carcinoma in Situ↗
PubMed1979

The formation and reaction of methyl radicals produced by direct photolysis of aqueous solutions of N-acetyl substituted aliphatic amino acids at 77K.

Photolysis of amino acids, peptides and their derivatives leads to the formation of free radicals in these substances. The electron-spin-resonance spectra obtained directly after irradiation at 77 K are not very well resolved. They are recognizable as the superposition of the spectra of different types of photoproduced radicals. CH3 radicals are formed by U.V. irradiation if methyl groups are present in the molecule. These radicals are easily detectable because of their four line spectrum. In this paper the formation of methyl radicals and their reaction with undamaged molecules of N-acetyl-substituted amino acids in investigated. The number of CH3 radicals present after a 30 min U.V. irradiation is higher if preceding U.V. irradiations and heat treatments are performed. The overall concentration of radicals is reduced only partially during this heat-treatment, while the CH3 radicals decay completely. Other experiments show that the rate of and the yield of CH3 radicals by U.V. irradiation increase with the dose of a preceding gamma-irradiation. The results suggest that there are substances present which are responsible for the higher production rate of methyl radicals after a preceding treatment. It is assumed that radicals are precursors of the fast-formed CH3 radicals

Amino Acids↗
PubMed1977

ESR an optical absorption studies on the copper(II) interaction with small peptides containing aromatic amino acids.

The interaction of Cu(II) with di- and tripeptides each containing phenylalanine, tryptophan or histidine in the amino acid chain has been investigated by means of electron spin resonance (ESR) and optical absorption spectroscopy. Cu(II) complexes of dipeptides and tripeptides exhibit different magnetic and optical parameters. Dipeptide complexes have larger gparallel-values and smaller A parallel values than tripeptide complexes. When compared to dipeptide complexes, the d-d band of the central metal ion is blue shifted for tripeptide complexes. There are no significant difference in the behavior of Cu(II) peptide complexes containing phenylalanine or tryptophan. Complexes of histidine containing peptides, however, show modified spectra caused by the participation of the imidazole nitrogen in the coordination to Cu(II). The imidazole nitrogen seems to coordinate in-plane with other coordinating atoms or in an axial position depending on the kind of peptide.

Chelating Agents↗
PubMed1976

ESR and optical absorption studies on the copper (II) interaction with aromatic amino acids.

Electron spin resonance and optical absorption studies have been done in order to investigate the interaction between Cu2+ and aromatic amino acids in aqueous solution at 77 K and at room temperature as well. Depending on the concentration each aromatic amino acid can form two different kinds of complexes with Cu2+ which can be characterized by its ESR pattern. Additional information was obtained from optical d-d and CT transitions.

Amino Acids↗
PubMed1976

Photolysis of N-methyl and N-acetyl substituted amino acids.

Experiments on the production of free radicals in aqueous solutions of N-methyl and N-acetyl substituted amino acids by UV light are reported. The ESR spectra observed at 77 K show that the bond of the CH3- group of these substances is ruptured to a great deal compared with other bond ruptures producing paramagnetic centres. But in N-methyl substituted amino acids the methyl radical is less predominant than in N-acetyl substituted ones. At temperatures higher than 200 K the ESR spectra of all substances studied in our experiments are similar. It is supposed that a radical is formed with an unpaired spin near an oxygen atom.

Electron Spin Resonance Spectroscopy↗
PubMed1975

Triplet state quenching by photoinduced radicals in the sensitized ethanol photolysis.

UV irradiation of a rigid solution of 2-amino-pyrimidine in ethanol at 77 degrees K results in a sensitized production of ethyl radicals. The radicals are formed via a biphotonic process. The increase of the radical yield with irradiation time is directly correlated to a decrease of the number of triplet state molecules as detected by ESR. A kinetic model of the biphotonic process is presented and verified by experimental results. It supports the hypothesis of a catalytically enhanced radiationless decay process of the triplet states due to an interaction between the radicals and the triplet state molecules.

Energy Transfer↗
PubMedDate not supplied

On the influence of aromatic residues on the interaction of copper (II) with small peptides containing aromatic amino acids: ESR and optical studies.

The complexation behaviour of Cu(II) with di- and tripeptides containing the aromatic amino acids phenylalanine or typtophan has been investigated at different pH-values and compared with results obtained with di- and triglycine. The results obtained by means of ESR and optical absorption spectroscopy show an influence of the two different aromatic entities on the magnetic and optical parameters. A significant decrease of the g11-value and, concomittantly, an increase of the energy of the d-d transition was measured when an aromatic entity is present in the peptide. A possible explanation for this observation is given.

Copper↗
PubMedDate not supplied

ESR investigations on lyophilized blood: mixtures with ascorbic acid.

The main contribution to ESR spectra of lyophilized tissues of plant or animal origin usually is given by an anisotropic singlet, which is known to be caused at least in the majority of cases by the adsorption of an ascorbyl radical. Model systems have been investigated in order to discuss experimental parameters, which influence these spectra qualitatively and quantitatively.

Ascorbic Acid↗