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Biomedical subjects

M Bolte

Publications and source records attributed to M Bolte.

At least 19 recordsLinked to original sources
PubMed2005

Self-trapping of magnetic oscillation modes in Landau flux-closure structures.

We investigated the magnetodynamics in rectangular Permalloy platelets by means of time-resolved x-ray photoemission microscopy. 10 nm thick platelets of size 16 x 32 microm were excited by an oscillatory field along the short side of the sample with a fundamental frequency of 500 MHz and considerable contributions of higher harmonics. Under the influence of the oscillatory field, the Néel wall in the initial classical Landau pattern shifts away from the center, corresponding to an induced magnetic moment perpendicular to the exciting field. This phenomenon is explained by a self-trapping effect of the dominating spin-wave mode when the system is excited just below the resonance frequency. The basic driving mechanism is the maximization of entropy.

Journal Article↗
PubMed2004

Degradation of 4-chlorophenol mediated by Fe(III)-NTA in homogeneous and heterogeneous systems.

In this work, the comparison of 4-chlorophenol (4-CP) degradation by two different AOT processes has been performed: a) a homogeneous system with Fe(III)-NTA (1:1 complex), b) a TiO2/Fe(III)-NTA heterogeneous system. In both cases, NTA appears to play a positive role in the photochemical reaction. In the homogeneous system, the iron salt is the only absorbing species and is proved to be able to photoinduce 4-CP degradation ([4-CP] = 0.1-0.2 mM, [FeNTA] = 0.3-0.9 mM, pH 4, lambda = 365 nm). The progress of the reaction was positively affected by the FeNTA concentration, and the reaction kept going even after the total disappearance of FeNTA. However, 4-CP complete degradation requires the presence of oxygen, otherwise the reaction stops. In the heterogeneous system ([4-CP] = 2.0 mM, [FeNTA] = 1.0-2.0 mM, [TiO2] = 0.1 and 1.0 g L(-1), pH 3, lambda = 300-400 nm), an important effect of the complex on the degradation extent and on the initial reaction rate can be seen, which overcomes the effect of non-complexed Fe(III). This behaviour is more important at the highest TiO2 concentration.

Chlorophenols↗
PubMed2004

Homogeneous (Fe(III)) and heterogeneous (TiO2) photocatalytic systems for pollutant removal from the aquatic compartment: comparison and complementarity.

Kinetics of the oxidative photodegradation of monuron (3-(4-chlorophenyl)-1-1-dimethylurea) in both homogeneous solution of Fe(ClO4)3 and heterogeneous suspension of TiO2, were investigated and compared. In the homogeneous system (Fe(II)), the speciation of Fe(III) aquacomplexes was shown to play an essential role in the rate of photodegradation. For high concentrations of TiO2 (> 500 mg L(-1)), the photodegradation rate was similar to the reaction rate obtained with a freshly prepared solution of Fe(II) (3 x 10(-4) mol L(-1)). In the combined system (TiO2 + Fe(III)), a synergy effect accelerating the monuron photodegradation was observed. Actually, in the presence of Fe(III) (in concentration compatible with a safe environment), a similar reaction rate for monuron photodegradation was obtained with a TiO2 concentration lower by a factor of 20.

Catalysis↗
PubMed2002

[Precurarization of succinylcholine with cisatracurium: the influence of the precurarization interval].

PURPOSE: To determine the influence of two different pretreatment intervals, i.e. 3 and 6 min, on the efficacy of 0.01 mg/kg cisatracurium in preventing succinylcholine-induced fasciculations and myalgia. METHODS: A total of 60 adult patients were randomized and received either 0.01 mg/kg cisatracurium (0.2*ED(95)) i.v. (Cis 3 group: pretreatment interval 3 min, Cis 6 group: pretreatment interval 6 min) or normal saline i.v. (placebo group) prior to injection of succinylcholine. The incidence and severity of fasciculations and myalgia and side-effects of precurarization were assessed. RESULTS: The incidence of muscle fasciculations was only reduced in the Cis 6 group (45%) compared with the Placebo group (85%), p<0.05. Cisatracurium was associated with a higher incidence of paralytic symptoms in both pretreatment groups (Cis 3: 75%, Cis 6: 80%) compared with the Placebo group (30%), p<0.05. CONCLUSION: Cisatracurium is only effective in preventing succinylcholine-induced fasciculations when a longer pretreatment interval, i.e. 6 min instead of 3 min, is chosen. Precurarization led to signs of paralysis in both pretreatment groups in the majority (75-80%) of patients without reducing the incidence or severity of postoperative myalgia.

Adult↗
PubMed2001

Two stereoisomeric 3(I),2(II)-anhydro-alpha-cyclodextrins: a molecular dynamics and crystallographic study.

Regioselective epoxide ring opening of 2(I),3(I)-(2(I)S)-anhydro-alpha-cyclodextrin (1) through intramolecular attack of hydroxyl groups of neighboring glucose rings occurs in diequatorial fashion to yield 3(I),2(II)-anhydro-alpha-cyclodextrin (3) with a rigid glucopyranose-dioxane-glucopyranose tricyclic ring system, the usual diaxial opening and the gluco/altro-configured stereoisomer 2 cannot be detected. Molecular dynamic simulations in water were used to analyze the conformations of 1-3 and the stereochemical implications of this reaction. Due to the contracted 2,3-OH side of the torus, 3 features an inverted conicity compared to the parent alpha-cyclodextrin. A crystallographic study on the bis-3.3 n-PrOH nonahydrate not only displays little variations between the solid-state and solution geometries of 3, but also provides a molecular picture of a unique inclusion complex in which three n-propanol molecules are distributed in the cavity of a dimeric unit of 3 (monoclinic, space group P2(1), a=14.257(1), b=22.623(2), c=16.644(1) A, beta=104.82(1) degrees, all 19,278 reflections with I>2 sigma(I) yield R(F)=0.1017).

Computer Simulation↗
PubMed2001

N-tert-Butyl-N'-(5,7-dimethyl-1,8-naphthyridin-2-yl)urea.

The title compound, C(15)H(20)N(4)O, has been synthesized as an AADD recognition unit for quadruple hydrogen bonds. All non-H atoms of the molecule apart from two methyl groups of the tert-butyl group lie in a common plane. An intramolecular hydrogen bond is formed connecting two N atoms. In the solid state, the title compound crystallizes as a centrosymmetric dimer connected by N-H...O=C interactions with an N...O distance of 2.824 (2) A.

Journal Article↗
PubMed2001

Dimorphism of ethyl 1,4-dihydro-2,4,6-triphenylpyridine-3-carboxylate.

The title compound, C26H23NO2, (Ia) and (Ib), shows polymorphism with crystals obtained from different solvents displaying different crystal structures. However, it is not the geometry of the single molecules nor the hydrogen-bond pattern that is different in (Ia) and (Ib), but the way in which the hydrogen-bonded chains, running along the a-axis direction, are arranged with respect to each other.

Crystallography, X-Ray↗
PubMed2001

3-Chlorophenol elimination upon excitation of dilute iron(III) solution: evidence for the only involvement of Fe(OH)2+.

The transformation of 3-chlorophenol (3CP) photoinduced by iron(II) in aqueous solution has been investigated under monochromatic irradiation (lambda(exc) = 365 nm) representative of atmospheric solar emission. Hydroxyl radicals are formed via an intramolecular photoredox process in iron(III) excited hydroxy-complexes. Fe(OH)2+ is the most active complex in terms of HO* formation and according to our experiments and calculations, it appears that Fe(OH)2+ is the only iron(III) species involved in 3CP oxidation process. Hydroxyl radicals react very rapidly with 3CP, which is eliminated from the solution. The primary intermediates do not accumulate in the medium but rapidly degraded to non-absorbing compounds by a subsequent action of hydroxyl radicals.

Chlorophenols↗
PubMed2001

Human trophoblast contains an intracellular protein reactive with an antibody against CD133--a novel marker for trophoblast.

CD133 is a protein expressed on the cell membrane of a subfraction of haematopoietic stem and progenitor cells, as well as on some epithelial cells. Previously available antibodies against CD133 recognized only the glycosylated protein, localized to membrane protrusions or microvilli. Due to this, immature intracellular stages of the CD133 protein could not be visualized using these antibodies. We describe reactivity of a commercially available antibody against CD133, called AC133-2, with an intracellular protein in trophoblast. Both villous and extravillous cytotrophoblast, as well as syncytiotrophoblast were stained by AC133-2 in cryostat sections of first trimester and term placenta. Villous stroma was not stained. AC133-2 reactivity was seen in methanol-fixed primary trophoblast cells and trophoblast-derived cell lines, and was coexpressed with cytokeratin-7. CD133 messenger RNA was present in trophoblast and trophoblast-derived cell lines, but also in cells not displaying any reactivity with CD133 antibodies. AC133-2 recognized a 55-60 kDa protein on Western blots of cell extracts including trophoblast. The exact nature of this protein is not yet understood. However, AC133-2 is applicable as a positive marker for the characterization of all subtypes of trophoblast and for trophoblast cell lines.

AC133 Antigen↗
PubMed2001

Dimethyl dispiro[tricyclo[3.3.1.1(3,7)]-decane-1,2'-bicyclo[1.1.0]butane-4',1"-tricyclo[3.3.1.1(3,7)]decane-1',3'-dicarboxylate, a strain-enhanced bicyclo[1.1.0]butane with a very short intramolecular C--H...H--C contact.

The title molecule, C(26)H(34)O(4), shows a very short repulsive intramolecular C-H.H-C contact, with an H.H distance of only 1.71 A. The flap angle varphi of the bicyclo[1.1.0]butane group is widened to 131.23 (8) degrees. Both methylene C atoms show tilt angles of 6.1 degrees. Bond lengths in the fused cyclopropane rings range from 1.501 (1) to 1.542 (1) A and are influenced by pi interactions with the carboxylate substituents.

Journal Article↗
PubMed2001

Two diastereomers of 9-(2,6-dichlorophenyl)-4a-hydroxy-3,3,6,6-tetramethyl-1,2,3,4,4a,5,6,7,8,9a-decahydroxanthene-1,8-dione in the same crystal.

The reaction of dimedone with 2,6-dichlorobenzaldehyde leads to the title compound, C(23)H(26)Cl(2)O(4). In principle, the reaction could yield eight different stereoisomers. We have found four of them in the same crystal as two enantiomeric pairs of diastereomers, which means that the asymmetric unit is built up of two different diastereomers. Two of the three chiral centres display the same configuration, while the third is different in the two molecules in the asymmetric unit. The packing of the molecules is stabilized by hydrogen bonds between the hydroxy group and the carbonyl group attached to the cyclohexene ring, forming chains in which the different diastereomers alternate.

Journal Article↗
PubMed2001

Packing considerations of bis-dimedone derivatives.

We have determined the crystal structures of 2,2'-(4-fluorophenyl)methylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexen-1-one), C(23)H(27)FO(4), (I), 2,2'-(4-chlorophenyl)methylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexen-1-one), C(23)H(27)ClO(4), (II), 2,2'-(4-hydroxyphenyl)methylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexen-1-one), C(23)H(28)O(5), (III), 2,2'-(4-methylphenyl)methylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexen-1-one), C(24)H(30)O(4), (IV), 2,2'-(4-methoxyphenyl)methylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexen-1-one), C(24)H(30)O(5), (V), and 2,2'-(4-N,N'-dimethylaminophenyl)methylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexen-1-one), C(25)H(33)NO(4), (VI). Structures (III) to (VI) of these bis-dimedone derivatives show nearly the same packing pattern irrespective of the different substituent in the para position of the aromatic ring. However, (II) does not fit into this scheme, although the Cl atom is a substituent not too different from the others. The different packing of the fluoro compound, (I), can be explained by the fact that it crystallizes with two molecules in the asymmetric unit, which show a different conformation of the dimedone ring. On the other hand, (I) shows a similar packing pattern to bis(2-hydroxy-4,4-dimethyl-6-oxo-1-cyclohexenyl)phenylmethane, a compound containing an aromatic ring without any substituent and with Z' = 2.

Journal Article↗
PubMed2000

Diethyl 9,10-dihydro-9,10-ethanoanthracene-11,12-trans-dicarboxylate.

The title compound, C(22)H(22)O(4), is the product of the Diels-Alder reaction of anthracene with fumaric acid diethyl ester. The molecular C(2) symmetry is nearly fulfilled in the crystal. Only the terminal torsion angles about the O-CH(2) groups show significant differences.

Journal Article↗
PubMed2000

4-Phenylbutan-2-one semicarbazone.

The title compound, C(11)H(15)N(3)O, crystallizes with two molecules in the asymmetric unit, which are held together by an extended network of hydrogen bonds. It is remarkable that only five of the six theoretically possible hydrogen bonds are formed.

Journal Article↗
PubMed2000

1,2,4-Triazolo[2,3-h]-7,9-thiaza-11-crown-4.

The title compound, 4,7-dioxa-10-thia-1,12,13-triazabicyclo[9.3.0]tetradeca-11,13-diene, C(8)H(13)N(3)O(2)S, contains an 11-membered ring, which appears in a chair conformation and has approximate mirror symmetry. It may be used for the complexation of metal atoms.

Journal Article↗