Search

Contains fulltext : 172141.pdf (Publisher’s version ) (Open Access), Antitumor immunity can be enhanced by the coordinated release and delivery of antigens and immune-stimulating agents to antigen-presenting cells via biodegradable vaccine carriers. So far, encapsulation of TLR ligands and tumor-associated antigens augmented cytotoxic T cell (CTLs) responses. Here, we compared the efficacy of the invariant NKT (iNKT) cell agonist alpha-galactosylceramide (alpha-GalCer) and TLR ligands (R848 and poly I:C) as an adjuvant for the full length ovalbumin (OVA) in PLGA nanoparticles. We observed that OVA+alpha-GalCer nanoparticles (NP) are superior over OVA+TLR-L NP in generating and stimulating antigen-specific cytotoxic T lymphocytes without the need for CD4+ T cell help. Not only a 4-fold higher induction of antigen-specific T cells was observed, but also a more profound IFN-gamma secretion was obtained by the addition alpha-GalCer. Surprisingly, we observed that mixtures of OVA containing NP with alpha-GalCer were ineffective, demonstrating that co-encapsulation of both alpha-GalCer and antigen within the same nanoparticle is essential for the observed T cell responses. Moreover, a single immunization with OVA+alpha-GalCer NP provided substantial protection from tumor formation and even delayed the growth of already established tumors, which coincided with a prominent and enhanced antigen-specific CD8+ T cell infiltration. The provided evidence on the advantage of antigen and alpha-GalCer coencapsulation should be considered in the design of future nanoparticle vaccines for therapeutic purposes.

Contains fulltext : 172141.pdf (Publisher’s version ) (Open Access), Antitumor immunity can be enhanced by the coordinated release and delivery of antigens and immune-stimulating agents to antigen-presenting cells via biodegradable vaccine carriers. So far, encapsulation of TLR ligands and tumor-associated antigens augmented cytotoxic T cell (CTLs) responses. Here, we compared the efficacy of the invariant NKT (iNKT) cell agonist alpha-galactosylceramide (alpha-GalCer) and TLR ligands (R848 and poly I:C) as an adjuvant for the full length ovalbumin (OVA) in PLGA nanoparticles. We observed that OVA+alpha-GalCer nanoparticles (NP) are superior over OVA+TLR-L NP in generating and stimulating antigen-specific cytotoxic T lymphocytes without the need for CD4+ T cell help. Not only a 4-fold higher induction of antigen-specific T cells was observed, but also a more profound IFN-gamma secretion was obtained by the addition alpha-GalCer. Surprisingly, we observed that mixtures of OVA containing NP with alpha-GalCer were ineffective, demonstrating that co-encapsulation of both alpha-GalCer and antigen within the same nanoparticle is essential for the observed T cell responses. Moreover, a single immunization with OVA+alpha-GalCer NP provided substantial protection from tumor formation and even delayed the growth of already established tumors, which coincided with a prominent and enhanced antigen-specific CD8+ T cell infiltration. The provided evidence on the advantage of antigen and alpha-GalCer coencapsulation should be considered in the design of future nanoparticle vaccines for therapeutic purposes.

Contains fulltext : 172141.pdf (Publisher’s version ) (Open Access), Antitumor immunity can be enhanced by the coordinated release and delivery of antigens and immune-stimulating agents to antigen-presenting cells via biodegradable vaccine carriers. So far, encapsulation of TLR ligands and tumor-associated antigens augmented cytotoxic T cell (CTLs) responses. Here, we compared the efficacy of the invariant NKT (iNKT) cell agonist alpha-galactosylceramide (alpha-GalCer) and TLR ligands (R848 and poly I:C) as an adjuvant for the full length ovalbumin (OVA) in PLGA nanoparticles. We observed that OVA+alpha-GalCer nanoparticles (NP) are superior over OVA+TLR-L NP in generating and stimulating antigen-specific cytotoxic T lymphocytes without the need for CD4+ T cell help. Not only a 4-fold higher induction of antigen-specific T cells was observed, but also a more profound IFN-gamma secretion was obtained by the addition alpha-GalCer. Surprisingly, we observed that mixtures of OVA containing NP with alpha-GalCer were ineffective, demonstrating that co-encapsulation of both alpha-GalCer and antigen within the same nanoparticle is essential for the observed T cell responses. Moreover, a single immunization with OVA+alpha-GalCer NP provided substantial protection from tumor formation and even delayed the growth of already established tumors, which coincided with a prominent and enhanced antigen-specific CD8+ T cell infiltration. The provided evidence on the advantage of antigen and alpha-GalCer coencapsulation should be considered in the design of future nanoparticle vaccines for therapeutic purposes.

Contains fulltext : 154084.pdf (publisher's version ) (Closed access), Sialic acid sugars are overexpressed by cancer cells and contribute to the metastatic cascade at multiple levels. Therapeutic interference of sialic acids, however, has been difficult to pursue because of the absence of dedicated tools. Here we show that a rationally designed sialic acid-blocking glycomimetic (P-3F(ax)-Neu5Ac) successfully prevents cancer metastasis. Formulation of P-3F(ax)--Neu5Ac into poly(lactic-co-glycolic acid nanoparticles coated with antityrosinase-related protein-1 antibodies allowed targeted delivery of P-3F(ax)--Neu5Ac into melanoma cells, slow release, and long-term sialic acid blockade. Most importantly, intravenous injections of melanoma-targeting P-3F(ax)--Neu5Ac nanoparticles prevented metastasis formation in a murine lung metastasis model. These findings stress the importance of sialoglycans in cancer metastasis and advocate that sialic acid blockade using rationally designed glycomimetics targeted to cancer cells can effectively prevent cancer metastases. This targeting strategy to interfere with sialic acid-dependent processes is broadly applicable not only for different types of cancer but also in infection and inflammation.

Item does not contain fulltext, Novel approaches of dendritic cell (DC) based cancer immunotherapy aim at harnessing the unique attributes of different DC subsets. Classical monocyte-derived DC vaccines are currently being replaced by either applying primary DCs or specifically targeting antigens and adjuvants to these subsets in vivo. Appropriate DC activation in both strategies is essential for optimal effect. For this purpose TLR agonists are favorable adjuvant choices, with TLR7 triggering being essential for inducing strong Th1 responses. However, mouse CD8alpha(+) DCs, considered to be the major cross-presenting subset, lack TLR7 expression. Interestingly, this DC subset can respond to TLR7 ligand upon concurrent TLR3 triggering. Nevertheless, the mechanism underlying this synergy remains obscure. We now show that TLR3 ligation results in the production of IFN-alpha, which rapidly induces the expression of TLR7, resulting in synergistic activation. Moreover, we demonstrate that this mechanism conversely holds for plasmacytoid DCs that respond to TLR3 ligation when TLR7 pathway is mobilized. We further demonstrate that this mechanism of sharpening DC senses is also conserved in human BDCA1(+) DCs and plasmacytoid DCs. These findings have important implications for future clinical trials as it suggests that combinations of TLR ligands should be applied irrespective of initial TLR expression profiles on natural DC subsets for optimal stimulation.

Contains fulltext : 154084.pdf (publisher's version ) (Closed access), Sialic acid sugars are overexpressed by cancer cells and contribute to the metastatic cascade at multiple levels. Therapeutic interference of sialic acids, however, has been difficult to pursue because of the absence of dedicated tools. Here we show that a rationally designed sialic acid-blocking glycomimetic (P-3F(ax)-Neu5Ac) successfully prevents cancer metastasis. Formulation of P-3F(ax)--Neu5Ac into poly(lactic-co-glycolic acid nanoparticles coated with antityrosinase-related protein-1 antibodies allowed targeted delivery of P-3F(ax)--Neu5Ac into melanoma cells, slow release, and long-term sialic acid blockade. Most importantly, intravenous injections of melanoma-targeting P-3F(ax)--Neu5Ac nanoparticles prevented metastasis formation in a murine lung metastasis model. These findings stress the importance of sialoglycans in cancer metastasis and advocate that sialic acid blockade using rationally designed glycomimetics targeted to cancer cells can effectively prevent cancer metastases. This targeting strategy to interfere with sialic acid-dependent processes is broadly applicable not only for different types of cancer but also in infection and inflammation.

Item does not contain fulltext, Novel approaches of dendritic cell (DC) based cancer immunotherapy aim at harnessing the unique attributes of different DC subsets. Classical monocyte-derived DC vaccines are currently being replaced by either applying primary DCs or specifically targeting antigens and adjuvants to these subsets in vivo. Appropriate DC activation in both strategies is essential for optimal effect. For this purpose TLR agonists are favorable adjuvant choices, with TLR7 triggering being essential for inducing strong Th1 responses. However, mouse CD8alpha(+) DCs, considered to be the major cross-presenting subset, lack TLR7 expression. Interestingly, this DC subset can respond to TLR7 ligand upon concurrent TLR3 triggering. Nevertheless, the mechanism underlying this synergy remains obscure. We now show that TLR3 ligation results in the production of IFN-alpha, which rapidly induces the expression of TLR7, resulting in synergistic activation. Moreover, we demonstrate that this mechanism conversely holds for plasmacytoid DCs that respond to TLR3 ligation when TLR7 pathway is mobilized. We further demonstrate that this mechanism of sharpening DC senses is also conserved in human BDCA1(+) DCs and plasmacytoid DCs. These findings have important implications for future clinical trials as it suggests that combinations of TLR ligands should be applied irrespective of initial TLR expression profiles on natural DC subsets for optimal stimulation.

Contains fulltext : 154363.pdf (Publisher’s version ) (Open Access), Novel approaches of dendritic cell (DC) based cancer immunotherapy aim at harnessing the unique attributes of different DC subsets. Classical monocyte-derived DC vaccines are currently being replaced by either applying primary DCs or specifically targeting antigens and adjuvants to these subsets in vivo. Appropriate DC activation in both strategies is essential for optimal effect. For this purpose TLR agonists are favorable adjuvant choices, with TLR7 triggering being essential for inducing strong Th1 responses. However, mouse CD8alpha(+) DCs, considered to be the major cross-presenting subset, lack TLR7 expression. Interestingly, this DC subset can respond to TLR7 ligand upon concurrent TLR3 triggering. Nevertheless, the mechanism underlying this synergy remains obscure. We now show that TLR3 ligation results in the production of IFN-alpha, which rapidly induces the expression of TLR7, resulting in synergistic activation. Moreover, we demonstrate that this mechanism conversely holds for plasmacytoid DCs that respond to TLR3 ligation when TLR7 pathway is mobilized. We further demonstrate that this mechanism of sharpening DC senses is also conserved in human BDCA1(+) DCs and plasmacytoid DCs. These findings have important implications for future clinical trials as it suggests that combinations of TLR ligands should be applied irrespective of initial TLR expression profiles on natural DC subsets for optimal stimulation.

Contains fulltext : 154084.pdf (publisher's version ) (Closed access), Sialic acid sugars are overexpressed by cancer cells and contribute to the metastatic cascade at multiple levels. Therapeutic interference of sialic acids, however, has been difficult to pursue because of the absence of dedicated tools. Here we show that a rationally designed sialic acid-blocking glycomimetic (P-3F(ax)-Neu5Ac) successfully prevents cancer metastasis. Formulation of P-3F(ax)--Neu5Ac into poly(lactic-co-glycolic acid nanoparticles coated with antityrosinase-related protein-1 antibodies allowed targeted delivery of P-3F(ax)--Neu5Ac into melanoma cells, slow release, and long-term sialic acid blockade. Most importantly, intravenous injections of melanoma-targeting P-3F(ax)--Neu5Ac nanoparticles prevented metastasis formation in a murine lung metastasis model. These findings stress the importance of sialoglycans in cancer metastasis and advocate that sialic acid blockade using rationally designed glycomimetics targeted to cancer cells can effectively prevent cancer metastases. This targeting strategy to interfere with sialic acid-dependent processes is broadly applicable not only for different types of cancer but also in infection and inflammation.

Item does not contain fulltext, Cancer immunotherapy critically relies on the efficient presentation of tumor antigens to T-cells to elicit a potent anti-tumor immune response aimed at life-long protection against cancer recurrence. Recent advances in the nanovaccine field have now resulted in formulations that trigger strong anti-tumor responses. Nanovaccines are assemblies that are able to present tumor antigens and appropriate immune-stimulatory signals either directly to T-cells or indirectly via antigen-presenting dendritic cells. This review focuses on important aspects of nanovaccine design for dendritic cells, including the synergistic and cytosolic delivery of immunogenic compounds, as well as their passive and active targeting to dendritic cells. In addition, nanoparticles for direct T-cell activation are discussed, addressing features necessary to effectively mimic dendritic cell/T-cell interactions.

Item does not contain fulltext, Vaccination is among the most efficient forms of immunotherapy. Although sometimes inducing lifelong protective B-cell responses, T-cell-mediated immunity remains challenging. Targeting antigen to dendritic cells (DCs) is an extensively explored concept aimed at improving cellular immunity. The identification of various DC subsets with distinct functional characteristics now allows for the fine-tuning of targeting strategies. Although some of these DC subsets are regarded as superior for (cross-) priming of naive T cells, controversies still remain about which subset represents the best target for immunotherapy. Because targeting the antigen alone may not be sufficient to obtain effective T-cell responses, delivery systems have been developed to target multiple vaccine components to DCs. In this Perspective, we discuss the pros and cons of targeting DCs: if targeting is beneficial at all and which vaccine vehicles and immunization routes represent promising strategies to reach and activate DCs.

Item does not contain fulltext, Cancer immunotherapy critically relies on the efficient presentation of tumor antigens to T-cells to elicit a potent anti-tumor immune response aimed at life-long protection against cancer recurrence. Recent advances in the nanovaccine field have now resulted in formulations that trigger strong anti-tumor responses. Nanovaccines are assemblies that are able to present tumor antigens and appropriate immune-stimulatory signals either directly to T-cells or indirectly via antigen-presenting dendritic cells. This review focuses on important aspects of nanovaccine design for dendritic cells, including the synergistic and cytosolic delivery of immunogenic compounds, as well as their passive and active targeting to dendritic cells. In addition, nanoparticles for direct T-cell activation are discussed, addressing features necessary to effectively mimic dendritic cell/T-cell interactions.

Item does not contain fulltext, Vaccination is among the most efficient forms of immunotherapy. Although sometimes inducing lifelong protective B-cell responses, T-cell-mediated immunity remains challenging. Targeting antigen to dendritic cells (DCs) is an extensively explored concept aimed at improving cellular immunity. The identification of various DC subsets with distinct functional characteristics now allows for the fine-tuning of targeting strategies. Although some of these DC subsets are regarded as superior for (cross-) priming of naive T cells, controversies still remain about which subset represents the best target for immunotherapy. Because targeting the antigen alone may not be sufficient to obtain effective T-cell responses, delivery systems have been developed to target multiple vaccine components to DCs. In this Perspective, we discuss the pros and cons of targeting DCs: if targeting is beneficial at all and which vaccine vehicles and immunization routes represent promising strategies to reach and activate DCs.

Item does not contain fulltext, Vaccination is among the most efficient forms of immunotherapy. Although sometimes inducing lifelong protective B-cell responses, T-cell-mediated immunity remains challenging. Targeting antigen to dendritic cells (DCs) is an extensively explored concept aimed at improving cellular immunity. The identification of various DC subsets with distinct functional characteristics now allows for the fine-tuning of targeting strategies. Although some of these DC subsets are regarded as superior for (cross-) priming of naive T cells, controversies still remain about which subset represents the best target for immunotherapy. Because targeting the antigen alone may not be sufficient to obtain effective T-cell responses, delivery systems have been developed to target multiple vaccine components to DCs. In this Perspective, we discuss the pros and cons of targeting DCs: if targeting is beneficial at all and which vaccine vehicles and immunization routes represent promising strategies to reach and activate DCs.

Contains fulltext : 109503.pdf (publisher's version ) (Open Access), Antibody-antigen conjugates, which promote antigen-presentation by dendritic cells (DC) by means of targeted delivery of antigen to particular DC subsets, represent a powerful vaccination approach. To ensure immunity rather than tolerance induction the co-administration of a suitable adjuvant is paramount. However, co-administration of unlinked adjuvant cannot ensure that all cells targeted by the antibody conjugates are appropriately activated. Furthermore, antigen-presenting cells (APC) that do not present the desired antigen are equally strongly activated and could prime undesired responses against self-antigens. We, therefore, were interested in exploring targeted co-delivery of antigen and adjuvant in cis in form of antibody-antigen-adjuvant conjugates for the induction of anti-tumour immunity. In this study, we report on the assembly and characterization of conjugates consisting of DEC205-specific antibody, the model antigen ovalbumin (OVA) and CpG oligodeoxynucleotides (ODN). We show that such conjugates are more potent at inducing cytotoxic T lymphocyte (CTL) responses than control conjugates mixed with soluble CpG. However, our study also reveals that the nucleic acid moiety of such antibody-antigen-adjuvant conjugates alters their binding and uptake and allows delivery of the antigen and the adjuvant to cells partially independently of DEC205. Nevertheless, antibody-antigen-adjuvant conjugates are superior to antibody-free antigen-adjuvant conjugates in priming CTL responses and efficiently induce anti-tumour immunity in the murine B16 pseudo-metastasis model. A better understanding of the role of the antibody moiety is required to inform future conjugate vaccination strategies for efficient induction of anti-tumour responses.

Item does not contain fulltext, CLEC9A is a recently discovered C-type lectin receptor involved in sensing necrotic cells. In humans, this receptor is selectively expressed by BDCA3(+) myeloid dendritic cells (mDCs), which have been proposed to be the main human cross-presenting mDCs and may represent the human homologue of murine CD8(+) DCs. In mice, it was demonstrated that antigens delivered with antibodies to CLEC9A are presented by CD8(+) DCs to both CD4(+) and CD8(+) T cells and induce antitumor immunity in a melanoma model. Here we assessed the ability of CLEC9A to mediate antigen presentation by human BDCA3(+) mDCs, which represent < 0.05% of peripheral blood leukocytes. We demonstrate that CLEC9A is only expressed on immature BDCA3(+) mDCs and that cell surface expression is lost after TLR-mediated maturation. CLEC9A triggering via antibody binding rapidly induces receptor internalization but does not affect TLR-induced cytokine production or expression of costimulatory molecules. More importantly, antigens delivered via CLEC9A antibodies to BDCA3(+) mDCs are presented by both MHC class I (cross-presentation) and MHC class II to antigen-specific T cells. We conclude that CLEC9A is a promising target for in vivo antigen delivery in humans to increase the efficiency of vaccines against infectious or malignant diseases.

Contains fulltext : 109503.pdf (publisher's version ) (Open Access), Antibody-antigen conjugates, which promote antigen-presentation by dendritic cells (DC) by means of targeted delivery of antigen to particular DC subsets, represent a powerful vaccination approach. To ensure immunity rather than tolerance induction the co-administration of a suitable adjuvant is paramount. However, co-administration of unlinked adjuvant cannot ensure that all cells targeted by the antibody conjugates are appropriately activated. Furthermore, antigen-presenting cells (APC) that do not present the desired antigen are equally strongly activated and could prime undesired responses against self-antigens. We, therefore, were interested in exploring targeted co-delivery of antigen and adjuvant in cis in form of antibody-antigen-adjuvant conjugates for the induction of anti-tumour immunity. In this study, we report on the assembly and characterization of conjugates consisting of DEC205-specific antibody, the model antigen ovalbumin (OVA) and CpG oligodeoxynucleotides (ODN). We show that such conjugates are more potent at inducing cytotoxic T lymphocyte (CTL) responses than control conjugates mixed with soluble CpG. However, our study also reveals that the nucleic acid moiety of such antibody-antigen-adjuvant conjugates alters their binding and uptake and allows delivery of the antigen and the adjuvant to cells partially independently of DEC205. Nevertheless, antibody-antigen-adjuvant conjugates are superior to antibody-free antigen-adjuvant conjugates in priming CTL responses and efficiently induce anti-tumour immunity in the murine B16 pseudo-metastasis model. A better understanding of the role of the antibody moiety is required to inform future conjugate vaccination strategies for efficient induction of anti-tumour responses.

Item does not contain fulltext, CLEC9A is a recently discovered C-type lectin receptor involved in sensing necrotic cells. In humans, this receptor is selectively expressed by BDCA3(+) myeloid dendritic cells (mDCs), which have been proposed to be the main human cross-presenting mDCs and may represent the human homologue of murine CD8(+) DCs. In mice, it was demonstrated that antigens delivered with antibodies to CLEC9A are presented by CD8(+) DCs to both CD4(+) and CD8(+) T cells and induce antitumor immunity in a melanoma model. Here we assessed the ability of CLEC9A to mediate antigen presentation by human BDCA3(+) mDCs, which represent < 0.05% of peripheral blood leukocytes. We demonstrate that CLEC9A is only expressed on immature BDCA3(+) mDCs and that cell surface expression is lost after TLR-mediated maturation. CLEC9A triggering via antibody binding rapidly induces receptor internalization but does not affect TLR-induced cytokine production or expression of costimulatory molecules. More importantly, antigens delivered via CLEC9A antibodies to BDCA3(+) mDCs are presented by both MHC class I (cross-presentation) and MHC class II to antigen-specific T cells. We conclude that CLEC9A is a promising target for in vivo antigen delivery in humans to increase the efficiency of vaccines against infectious or malignant diseases.

A sensitive, selective, and comprehensive method for the quantitative determination of tryptophan and 18 of its key metabolites in serum, urine, and cell culture supernatants was developed. The analytes were separated on a C18 silica column by reversed-phase liquid chromatography and detected by electrospray ionization tandem mass spectrometry in positive ion multiple reaction monitoring (MRM) mode, except for indoxyl sulfate which was measured in negative ion MRM mode in a separate run. The limits of detection and lower limits of quantification were in the range of 0.1–50 and 0.5–100 nM, respectively. Fully 13C isotope-labeled and deuterated internal standards were used to achieve accurate quantification. The applicability of the method to analyze serum, urine, and cell culture supernatants was demonstrated by recovery experiments and the evaluation of matrix effects. Precision for the analysis of serum, urine, and cell culture supernatants ranged between 1.3% and 16.0%, 1.5% and 13.5%, and 1.0% and 17.4%, respectively. The method was applied to analyze changes in tryptophan metabolism in cell culture supernatants from IFN-?-treated monocytes and immature or mature dendritic cells., Biotechnology, Applied Sciences

A sensitive, selective, and comprehensive method for the quantitative determination of tryptophan and 18 of its key metabolites in serum, urine, and cell culture supernatants was developed. The analytes were separated on a C18 silica column by reversed-phase liquid chromatography and detected by electrospray ionization tandem mass spectrometry in positive ion multiple reaction monitoring (MRM) mode, except for indoxyl sulfate which was measured in negative ion MRM mode in a separate run. The limits of detection and lower limits of quantification were in the range of 0.1–50 and 0.5–100 nM, respectively. Fully 13C isotope-labeled and deuterated internal standards were used to achieve accurate quantification. The applicability of the method to analyze serum, urine, and cell culture supernatants was demonstrated by recovery experiments and the evaluation of matrix effects. Precision for the analysis of serum, urine, and cell culture supernatants ranged between 1.3% and 16.0%, 1.5% and 13.5%, and 1.0% and 17.4%, respectively. The method was applied to analyze changes in tryptophan metabolism in cell culture supernatants from IFN-?-treated monocytes and immature or mature dendritic cells., Biotechnology, Applied Sciences

At the Helmholtz center GSI, PHELIX (Petawatt High Energy Laser for heavy Ion eXperiments) has been commissioned for operation in stand-alone mode and, in combination with ions accelerated up to an energy of 13 MeV/u by the heavy ion accelerator UNILAC. The combination of PHELIX with the heavy-ion beams available at GSI enables a large variety of unique experiments. Novel research opportunities are spanning from the study of ion–matter interaction, through challenging new experiments in atomic physics, nuclear physics, and astrophysics, into the field of relativistic plasma physics.

At the Helmholtz center GSI, PHELIX (Petawatt High Energy Laser for heavy Ion eXperiments) has been commissioned for operation in stand-alone mode and, in combination with ions accelerated up to an energy of 13 MeV/u by the heavy ion accelerator UNILAC. The combination of PHELIX with the heavy-ion beams available at GSI enables a large variety of unique experiments. Novel research opportunities are spanning from the study of ion–matter interaction, through challenging new experiments in atomic physics, nuclear physics, and astrophysics, into the field of relativistic plasma physics.

The nuclides 92Mo, 98Mo and 100Mo have been studied in photon-scattering experiments by using bremsstrahlung. Dipole and quadrupole excitations in 92Mo were investigated in photon-scattering experiments at an electron energy of 6 MeV at the ELBE accelerator of the Forschungszentrum Rossendorf. Photon-scattering experiments on 98Mo and 100Mo were carried out at the Dynamitron accelerator of the Stuttgart University at electron energies from 3.2 to 3.8 MeV. Six dipole transitions in 98Mo and 19 in 100Mo were observed for the first time in the energy range from 2 to 4 MeV. Systematics of the magnetic dipole strength in the isotopic chain of the even-mass isotopes from 92Mo to 100Mo are discussed. The experimental results are compared with predictions of the shell model and with predictions of the quasiparticle-random-phase approximation in a deformed basis. The latter show significant contributions of isovector-orbital and isovector-spin vibrations.

The nuclides 98Mo and100Mo have been studied in photon-scattering experiments by using bremsstrahlung produced from electron beams with energies from 3.2 to 3.8 MeV. Six dipole transitions in 98Mo and 19 in 100Mo were observed for the first time in the energy range from 2 to 4 MeV. A specific feature in both nuclides is the deexcitation of one state with spin J = 1 to the 0+ ground state as well as to the first excited 0+ state, which cannot be explained in standard models. We present a model based on one-particle-one-hole excitations, which allows us to deduce the mixing amplitudes for the two 0+ shape-isomeric states from the experimental ratio of the transition strengths from the J = 1 state to the 0+ ground state and to the 0+ excited state.