Biomedical subjects

Torben Lund

Publications and source records attributed to Torben Lund.

12 recordsLinked to original sources

PubMed2005

Determination of the light-induced degradation rate of the solar cell sensitizer N719 on TiO2 nanocrystalline particles.

The oxidative degradation rate, kdeg, of the solar cell dye (Bu4N+)2[Ru(dcbpyH)2(NCS)2]2-, referred to as N719 or [RuL2(NCS)2], was obtained by applying a simple model system. Colloidal solutions of N719-dyed TiO2 particles in acetonitrile were irradiated with 532-nm monochromatic light, and the sum of the quantum yields for the oxidative degradation products [RuL2(CN)2], [RuL2(NCS)(CN)], and [RuL2(NCS)(ACN)], Phideg, was obtained at eight different light intensities in the range of 0.1-16.30 mW/cm2 by LC-UV-MS. The Phideg values decreased from 3.3 x 10-3 to 2.0 x 10-4 in the applied intensity range. By using the relation kdeg = Phidegkback and back electron-transfer reaction rates, kback, obtained with photoinduced absorption spectroscopy, it was possible to calculate an average value for the oxidative degradation rate of N719 dye attached to TiO2 particles, kdeg = 4.0 x 10-2 s-1. The stability of N719 dye during solar cell operation was discussed based on this number, and on values of the electron-transfer rate between [Ru(III)L2(NCS)2] and iodide ion that are available in the literature.

Journal Article↗

PubMed2005

The human chorionic gonadotropin-beta arginine68 to glutamic acid substitution fixes the conformation of the C-terminal peptide.

Wild-type human chorionic gonadotropin (hCG) has been used as a contraceptive vaccine. However, extensive sequence homology with LH elicits production of cross-reactive antibodies. Substitution of arginine(68) of the beta-subunit (hCG(beta)) with glutamic acid (R68E) profoundly reduces the cross-reactivity while refocusing the immune response to the hCG(beta)-specific C-terminal peptide (CTP). To investigate the molecular basis for this change in epitope usage, we immunized mice with a plasmid encoding a truncated hCG(beta)-R68E chain lacking the CTP. The animals produced LH-cross-reactive antibodies, suggesting that the refocused immunogenicity of R68E is a consequence of epitope masking by a novel disposition of the CTP in the mutant rather than a structural change in the cross-reactive epitope region. This explanation was strongly supported by surface plasmon resonance analysis using a panel of anti-hCG(beta)-specific and anti-hCG(beta)/LH cross-reactive monoclonal antibodies (mAbs). Whereas the binding of the LH cross-reactive mAbs to hCG(beta)-R68E was eliminated, mAbs reacting with hCG(beta)-specific epitopes bound to hCG(beta) and hCG(beta)-R68E with identical affinities. In a separate series of experiments, we observed that LH cross-reactive epitopes were silent after immunization with a plasmid encoding a membrane form of hCG(beta)-R68E, as previously observed with the soluble mutant protein itself. In contrast, the plasmid encoding the soluble secreted form of hCG(beta)-R68E evoked LH cross-reactive antibodies, albeit of relatively low titer, suggesting that the handling and processing of the proteins produced by the two constructs differed.

Amino Acid Substitution↗

PubMed2004

DNA immunization with plasmids expressing hCGbeta-chimeras.

Human chorionic gonadotropin has been used as an anti-fertility vaccine and as a target for cancer immunotherapy. We have explored the use of DNA immunization with the aim of improving the immunogenicity of this hormone. Stimulating the muscle with electric pulses following intramuscular injection of plasmids expressing hCGbeta resulted in higher levels of human chorionic gonadotropin (hCG)-specific antibodies, which could be further enhanced following a protein boost with hCG mixed with adjuvant. DNA vaccines encoding a membrane attached or a secreted form of hCGbeta produced similar-albeit relatively modest-antibody responses. Providing hCGbeta with additional T cell help by vaccinating with a plasmid encoding a hCGbeta-hFc fusion protein did not further increase the antibody levels in the immunized animals. However, immunization of mice with a construct encoding hCGbeta fused to C3d(3) produced significantly lower antibody levels relative to mice immunized with the hCGbeta-alone expression plasmid, even though the hCGbeta-C3d(3) chimera was expected to facilitate cross-linking of the antigen-specific B-cell receptor and CR2 thereby lowering the threshold of activation. Thus the limiting factor determining the antibody levels following hCGbeta immunization, at least for DNA immunization, is related to the amount of protein available rather than the form of protein produced or lack of T cell epitopes.

Adjuvants, Immunologic↗

PubMed2003

Sensitive and selective analysis of coenzyme Q10 in human serum by negative APCI LC-MS.

Two new sensitive and selective LC-MS methods have been developed for the quantification of the total coenzyme Q(10) concentration in human blood serum. The sensitivity of the methods is based on the very efficient formation of the radical anions of CoQ(10)[M(-)[radical dot]] by negative atmospheric pressure ionisation, APCI(-). The mass detection of the [M(-)[radical dot]] ions, m/z= 862.6, was performed either in selective ion monitoring (SIM) or in MS(2) mode (m/z= 862.6 [rightward arrow]m/z= 847.6) using an LCQ-deca ion-trap mass spectrometer. Two standard serum samples with medium (0.73 [micro sign]g ml(-1)) and high (1.96 [micro sign]g ml(-1)) total CoQ(10) concentrations were analysed by LC-APCI(-)-SIM and LC-APCI(-)-MS(2) and the results compared with a HPLC literature procedure with electrochemical detection (ECD). Both the LC-MS methods were shown to be more selective and with comparable or better sensitivity than the HPLC-ECD method. The LC-MS-SIM and LC-MS(2) chromatograms of the medium concentration sample showed CoQ(10) signal to noise ratios of 25 and 625, respectively. In addition, a simple and fast serum pre-treatment procedure was developed, in which the serum CoQ(10)H(2) content was quantitatively oxidised quantitatively to CoQ(10) in less than 15 min by 1,4-benzoquinone.

Chromatography, Liquid↗

PubMed2003

Products of the electrochemical oxidation of cis-L(2)Ru((II))(NCS)(2) in dimethylformamide and acetonitrile determined by LC-UV/Vis-MS.

The bis tetrabutylammonium salt of the solar cell dye, L(2)Ru(NCS)(2), ((Bu(4)N(+))(2) [Ru(dcbpyH)(2)(NCS)(2)](2-)), was oxidized electrochemically in both dimethylformamide and acetonitrile. Four different ruthenium complexes were identified by LC-UV/Vis-MS during the electrochemical oxidation process in dimethylformamide. The formation of the four complexes may be explained by a competition between a solvent-independent route with the formation of the intermediate complex L(2)Ru(NCS)(CN) and the final oxidation product L(2)Ru(CN)(2) and a solvent-dependent route, which proceeds through the intermediate complex L(2)Ru(NCS)(DMF)(+) to the final product L(2)Ru(CN)(DMF)(+). In acetonitrile the solvent-dependent mechanism is dominant and only the oxidation products L(2)Ru(NCS)(ACN)(+) and L(2)Ru(CN)(ACN)(+) were identified.

Journal Article↗

PubMed2003

Direct determination of rate constants for coupling between aromatic radical anions and alkyl and benzyl radicals by laser-flash photolysis.

Coupling rates between the radicals methyl, n-, sec-, tert-butyl and benzyl (R.) and the aromatic radical anions of 1,4-dicyanonaphthalene, 9,10-dicyanoanthracene and fluorenone (A-.) have been obtained using a new laser-flash photolysis method. The radicals R. and the radical anions A-. were generated by a photoinduced electron transfer reaction between the aromatic compound A and the alkyl or benzyl triphenylborate anion RB(Ph)3-. For the first time the rate constants of the coupling reaction between methyl and benzyl radicals with aromatic radical anions have been obtained. For all the measured coupling rate constants an average value of k1 = 1.9 x 10(9) M-1 s-1 was found with a relatively small variation in the coupling rates (0.8-2.9 x 10(9) M-1 s-1). The results demonstrate that the coupling rate k1 is insensitive to changes in the steric and electronic properties of the radicals and the structure and standard potentials of the aromatic radical anions.

Journal Article↗

PubMed2003

Long-term effect of Sea-Nine on natural coastal phytoplankton communities assessed by pollution induced community tolerance.

Sea-Nine211 has been introduced as a new biocide in antifouling paints with an immediate degradation when it is released from ship hulls. The active component of Sea-Nine211 is 4,5-dichloro-2-n-octyl-isothiazoline-3-one (DCOI). In the present study, the toxicity of DCOI and the occurrence of Pollution Induced Community Tolerance (PICT) were tested in microcosms containing eutrophic coastal water with its natural composition of phytoplankton. The experiment was performed in closed systems with a single addition of the nominal concentrations 0, 3.2, 10, 32 and 100 nM DCOI, for a period of 16 days. Pollution induced community tolerance (PICT) was observed in the phytoplankton communities exposed to the nominal concentrations 32 and 100 nM DCOI. Chemical analysis of DCOI in the coastal water utilised in the toxicity and PICT experiment was performed by GC-MS using a solid- phase extraction method. Half-life was calculated to be 2.5 days for the nominal concentrations 32 and 100 nM DCOI. The results of the present study show that nominal concentrations of 32 and 100 nM DCOI significantly increased the community tolerance already after 2 days of exposure and that the tolerance was maintained for a period of 16 days even when DCOI was degraded during this period. The causes for the persistent tolerance are discussed in relation to the degradation of DCOI and structural changes in the phytoplankton communities.

Adaptation, Physiological↗

PubMed2002

Elimination of luteinizing hormone cross-reactive epitopes from human chorionic gonadotropin.

The beta-chain of human chorionic gonadotropin (hCG) has been shown to have efficacy in clinical trials when used as a contraceptive vaccine. This hormone is a heterodimer, the alpha-chain being shared with the other members of the glycoprotein hormone family but the beta-chain being unique to hCG. Nevertheless, there is sequence homology between the hCG beta-chain and the beta-chain of human luteinizing hormone (hLH) which results in cross-reactive antibodies being produced following immunization with wild-type hCGbeta. To reduce or eliminate such cross-reactions we generated a number of mutants of the hCGbeta-chain. One mutant (hCGbeta(R68E)), containing an arginine to glutamic acid replacement at position 68, has been expressed as a recombinant protein in High Five insect cells. The recombinant BAChCGbeta(R68E) form of this molecule was used to immunize rabbits and the antibody response compared to the response following immunization with the recombinant wild-type protein BAChCGbeta and with the native hCGalphabeta heterodimer isolated from pregnancy urine. The mutant elicited the production of antibodies which avidly recognize native hCG. Compared to immunization with wild-type hCG, the response showed very little cross reactivity with hLH. This is demonstrated to be due to a radically altered epitope usage in the response to the mutant, which now focuses mainly upon the C-terminal region of the beta-chain.

Animals↗

PubMed2002

Identification of 1-hydroxypyrene glucuronide in tissue of marine polychaete Nereis diversicolor by liquid chromatography/ion trap multiple mass spectrometry.

1-Hydroxypyrene glucuronide is identified as the single major aqueous metabolite of the tetracyclic aromatic hydrocarbon pyrene, in tissue from a deposit-feeding marine polychaete, Nereis diversicolor. Identification was performed using an ion trap mass spectrometer fitted with an atmospheric pressure chemical ionization (APCI) probe and connected to a high-performance liquid chromatography/diode array detector (HPLC/DAD) system. Besides 1-hydroxypyrene, the 339-nm UV trace of tissue samples from pyrene-exposed worms showed only one dominant peak that could be related to pyrene metabolism. Negative APCI-MS of this supposed 1- hydroxypyrene conjugate gave a characteristic signal at m/z 429 corresponding to the molecular ion of 1-hydroxypyrene glucuronide plus eluent adducts ([M - H + 2H(2)O](-)). Fragmentation pathways were studied by isolating the abundant ion at m/z 429 in the ion trap and performing multiple mass spectrometric experiments (MS(n)). The fragmentations observed were consistent with the proposed identification. Two low intensity LC peaks that could be related to pyrene metabolism by their DAD absorption spectra were also present in the 339-nm UV chromatogram of tissue samples. However, these peaks could not be identified by their mass spectra in negative ion mode due to ion suppression by very abundant co-eluting impurities. The present method shows that LC/MS(n) is a fast and useful analytical tool for identification of aqueous polycyclic aromatic hydrocarbon biotransformation products in samples from relatively small marine invertebrates with limited sample preparation.

Animals↗

PubMed2002

Antifertility vaccines.

The possibility of using immunization as a method of birth control has been explored actively since the 1930s, with several different sperm, egg or hormonal antigens having been studied as suitable targets for intervention. However, it is only in the past decade that the efficacy of vaccination against fertility has become established firmly in both humans and free-roaming animal populations. We will review recent progress in the continuing development of antifertility vaccines, with an emphasis on vaccines intended ultimately for use in humans, whilst highlighting also some of the notable successes achieved with vaccines produced for use in other species.

Animals↗

PubMed2002

Future prospects for vaccines to control fertility.

Vaccination is used routinely to protect against infectious disease and is being explored increasingly as a method of protection against tumors. Also, it has been established that vaccination using antigens associated with reproduction can protect against undesired pregnancy. Substantial progress over the past decade suggests that, if the remaining immunological and socioeconomic issues can be resolved, antifertility vaccines could be a valuable, additional method of family planning.

Clinical Trials as Topic↗

PubMedDate not supplied

Genetic regulation of mouse glycosylphosphatidylinositol-phospholipase D.

Glycosylphosphatidylinositol phospholipase D (GPI-PLD) has been proposed to be responsible for cleaving membrane-associated glycosylphosphatidyl inositol (GPI) molecules to generate inositol phosphoglycan (IPGs), which have growth factor-mimetic properties. We have cloned the mouse liver GPI-PLD cDNA, which has a sequence that differs from that previously isolated from a mouse glucagonoma cell library. Using a highly specific and very sensitive RNase protection assay, we found that the GPI-PLD expressed in adult/post-natal brain, antrum and insulin-producing cells is identical to that isolated from liver. The expression of mouse GPI-PLD in liver shows a complex genetic regulation with a mouse strain-specific variation. In addition, GPI-PLD mRNA levels were higher in 4-week old animals compared to older animals, and the GPI-PLD mRNA levels increased in mice that developed insulin dependent type 1 diabetes spontaneously. This suggests that the expression of liver GPI-PLD in mice is highly regulated.

Amino Acid Sequence↗