| 1. |
- Kragh Sørensen, Lasse, et al.
(författare)
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Nature of the Anomalous Size Dependence of Resonance Red Shifts in Ultrafine Plasmonic Nanoparticles
- 2022
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:39, s. 16804-16814
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Tidskriftsartikel (refereegranskat)abstract
- Plasmonic red shifts of nanoparticles are commonly used in imaging technologies to probe the character of local environments, and the understanding of their dependence on size, shape, and surrounding media has therefore become an important target for research. The red shift of plasmon resonances changes character at about 8-10 nm of size for spherical gold nanoparticles-above this value, the red shift progresses linearly with particle size, while below this size, the red shift changes nonlinearly and more strongly with size. Using an atomistic discrete interaction model, we have studied the special properties of the nanoparticle surface layers and discovered its importance for ultrafine plasmonic nanoparticles and their red shifts. We find that the physical origin for the specific properties inherent to the surface layer of atoms near the nanoparticle boundary is related to the anisotropy of the local environment of atoms in this layer by other atoms. The anisotropy changes the conditions for light-induced nonlocal interactions of neighboring atoms with each other and with the incident radiation compared to the atoms located in the particle core with isotropic nearest surroundings by other atoms. The local anisotropy of the nanoparticle crystal lattice is a geometric factor that increases toward its boundary and that is the most fundamental factor underlying the physical differences between the nanoparticle surface layer and the core material. It is shown that the inflexion point at 8-10 nm is due to a change in the dominant physical origin of the red shift -from chaotization of atomically light-induced dipoles within the surface layer in the case of ultrafine nanoparticles to retardation effects for large nanoparticles in which the relative volume of the surface layer decreases rapidly to a negligible value with increasing nanoparticle size. The patterns revealed are the basis for predicting the manifestation of surface layer effects in ultrafine plasmonic nanoparticles of different and of different materials.
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| 2. |
- Sørensen, Lasse K., et al.
(författare)
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Plasmonic Enhancement of Local Fields in Ultrafine Metal Nanoparticles
- 2021
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:25, s. 13900-13908
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Tidskriftsartikel (refereegranskat)abstract
- We present an analysis of ultrafine metallic nanoparticles (1-15 nm) with respect to electromagnetic field generation by plasmonic excitations. A number of structures with different symmetries and geometries are studied in order to analyze the distributions of plasmonically generated near-electric fields and the concentration of hot and cold spots around the particles. The study is made possible by the recent development of an extended discrete interaction model (Ex-DIM) where the explicit dependency of the plasmonic spectra on the structure and composition of particles in the range of 1-15 nm is accounted for. With the Ex-DIM, the optical response of the internal crystal structure of the nanoscale particles can be visualized, thereby making it possible to predict the dependence of the generated local fields with respect to the position of the particles relative to the external field polarization. The results indicate rather surprising concentrations of the plasmon fields in very confined hot spots also in cases when the particles retain a high symmetry. The consequence of the findings of this study when using small symmetric nanoparticles for near-field imaging is briefly discussed.
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| 3. |
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| 4. |
- Adl, Sina M., et al.
(författare)
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Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes
- 2019
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Ingår i: Journal of Eukaryotic Microbiology. - : WILEY. - 1066-5234 .- 1550-7408. ; 66:1, s. 4-119
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Tidskriftsartikel (refereegranskat)abstract
- This revision of the classification of eukaryotes follows that of Adl et al., 2012 [J. Euk. Microbiol. 59(5)] and retains an emphasis on protists. Changes since have improved the resolution of many nodes in phylogenetic analyses. For some clades even families are being clearly resolved. As we had predicted, environmental sampling in the intervening years has massively increased the genetic information at hand. Consequently, we have discovered novel clades, exciting new genera and uncovered a massive species level diversity beyond the morphological species descriptions. Several clades known from environmental samples only have now found their home. Sampling soils, deeper marine waters and the deep sea will continue to fill us with surprises. The main changes in this revision are the confirmation that eukaryotes form at least two domains, the loss of monophyly in the Excavata, robust support for the Haptista and Cryptista. We provide suggested primer sets for DNA sequences from environmental samples that are effective for each clade. We have provided a guide to trophic functional guilds in an appendix, to facilitate the interpretation of environmental samples, and a standardized taxonomic guide for East Asian users.
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| 5. |
- Latanova, Anastasia, et al.
(författare)
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Fusion to Flaviviral Leader Peptide Targets HIV-1 Reverse Transcriptase for Secretion and Reduces Its Enzymatic Activity and Ability to Induce Oxidative Stress but Has No Major Effects on Its Immunogenic Performance in DNA-Immunized Mice
- 2017
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Ingår i: Journal of Immunology Research. - : HINDAWI LTD. - 2314-8861 .- 2314-7156.
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Tidskriftsartikel (refereegranskat)abstract
- Reverse transcriptase (RT) is a key enzyme in viral replication and susceptibility to ART and a crucial target of immunotherapy against drug-resistant HIV-1. RT induces oxidative stress which undermines the attempts to make it immunogenic. We hypothesized that artificial secretion may reduce the stress and make RT more immunogenic. Inactivated multidrug-resistant RT (RT1.14opt-in) was N-terminally fused to the signal providing secretion of NS1 protein of TBEV (Ld) generating optimized inactivated Ld-carrying enzyme RT1.14oil. Promotion of secretion prohibited proteasomal degradation increasing the half-life and content of RT1.14oil in cells and cell culture medium, drastically reduced the residual polymerase activity, and downmodulated oxidative stress. BALB/c mice were DNA-immunized with RT1.14opt-in or parental RT1.14oil by intradermal injections with electroporation. Fluorospot and ELISA tests revealed that RT1.14opt-in and RT1.14oil induced IFN-gamma/IL-2, RT1.14opt-in induced granzyme B, and RT1.14oil induced perforin production. Perforin secretion correlated with coproduction of IFN-gamma and IL-2 (R = 0,97). Both DNA immunogens induced strong anti-RT antibody response. Ld peptide was not immunogenic. Thus, Ld-driven secretion inferred little change to RT performance in DNA immunization. Positive outcome was the abrogation of polymerase activity increasing safety of RT-based DNA vaccines. Identification of the molecular determinants of low cellular immunogenicity of RT requires further studies.
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| 6. |
- Saikova, Svetlana, et al.
(författare)
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Copper Ferrite Nanoparticles Synthesized Using Anion-Exchange Resin : Influence of Synthesis Parameters on the Cubic Phase Stability
- 2023
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Ingår i: Materials. - : MDPI. - 1996-1944. ; 16:6
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Tidskriftsartikel (refereegranskat)abstract
- Copper ferrite is of great interest to researchers as a material with unique magnetic, optical, catalytic, and structural properties. In particular, the magnetic properties of this material are structurally sensitive and can be tuned by changing the distribution of Cu and Fe cations in octahedral and tetrahedral positions by controlling the synthesis parameters. In this study, we propose a new, simple, and convenient method for the synthesis of copper ferrite nanoparticles using a strongly basic anion-exchange resin in the OH form. The effect and possible mechanism of polysaccharide addition on the elemental composition, yield, and particle size of CuFe2O4 are investigated and discussed. It is shown that anion-exchange resin precipitation leads to a mixture of unstable cubic (c-CuFe2O4) phases at standard temperature and stable tetragonal (t-CuFe2O4) phases. The effect of reaction conditions on the stability of c-CuFe2O4 is studied by temperature-dependent XRD measurements and discussed in terms of cation distribution, cooperative Jahn–Teller distortion, and Cu2+ and oxygen vacancies in the copper ferrite lattice. The observed differences in the values of the saturation magnetization and coercivity of the prepared samples are explained in terms of variations in the particle size and structural properties of copper ferrite.
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| 7. |
- Shadrina, Olga, et al.
(författare)
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Consensus HIV-1 subtype A integrase and its raltegravir-resistant variants: Design and characterization of the enzymatic properties.
- 2014
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Ingår i: Biochimie. - : Elsevier BV. - 1638-6183 .- 0300-9084. ; 102C:Mar 2, s. 92-101
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Tidskriftsartikel (refereegranskat)abstract
- Model studies of the subtype B and non-subtype B integrases are still required to compare their susceptibility to antiretroviral drugs, evaluate the significance of resistance mutations and identify the impact of natural polymorphisms on the level of enzymatic reactivity. We have therefore designed the consensus integrase of the HIV-1 subtype A strain circulating in the former Soviet Union territory (FSU-A) and two of its variants with mutations of resistance to the strand transfer inhibitor raltegravir. Their genes were synthesized, and expressed in E coli; corresponding His-tagged proteins were purified using the affinity chromatography. The enzymatic properties of the consensus integrases and their sensitivity to raltegravir were examined in a series of standard in vitro reactions and compared to the properties of the integrase of HIV-1 subtype B strain HXB2. The consensus enzyme demonstrated similar DNA-binding properties, but was significantly more active than HXB-2 integrase in the reactions of DNA cleavage and integration. All integrases were equally susceptible to inhibition by raltegravir and elvitegravir, indicating that the sporadic polymorphisms inherent to the HXB-2 enzyme have little effect on its susceptibility to drugs. Insensitivity of the mutated enzymes to the inhibitors of strand transfer occurred at a cost of a 30-90% loss of the efficacies of both 3'-processing and strand transfer. This is the first study to describe the enzymatic properties of the consensus integrase of HIV-1 clade A and the effects of the resistance mutations when the complex actions of sporadic sequence polymorphisms are excluded.
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| 8. |
- Tikhonenkov, Denis, V, et al.
(författare)
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On the origin of TSAR : morphology, diversity and phylogeny of Telonemia
- 2022
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Ingår i: Open Biology. - : The Royal Society. - 2046-2441. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- Telonemia is a poorly known major phylum of flagellated eukaryotes with a unique combination of morphological traits. Phylogenomics recently revealed the phylogenetic position of telonemids as sister to SAR, one of the largest groups of eukaryotes, comprising Stramenopiles, Alveolata and Rhizaria. Due to this key evolutionary position, investigations of telonemids are of critical importance for elucidating the origin and diversification of an astounding diversity of eukaryotic forms and life strategies. To date, however, only two species have been morphologically characterized from Telonemia, which do not represent this genetically very diverse group. In this study, we established cultures for six new telonemid strains, including the description of five new species and a new genus. We used these cultures to update the phylogeny of Telonemia and provide a detailed morphological and ultrastructural investigation. Our data elucidate the origin of TSAR from flagellates with complex morphology and reconstruction of the ancestral structure of stramenopiles, alveolates and rhizarians, and their main synapomorphic characters. Since telonemids are a common component of aquatic environments, the features of their feeding, behaviour and ecological preferences observed in clonal cultures and the results of global metabarcoding analysis contribute to a deeper understanding of organization of microbial food webs.
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| 9. |
- Zakomirnyi, Vadim, et al.
(författare)
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Collective lattice resonances in arrays of dielectric nanoparticles : a matter of size
- 2019
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Ingår i: Optics Letters. - : OSA - The Optical Society. - 0146-9592 .- 1539-4794. ; 44:23, s. 5743-5746
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Tidskriftsartikel (refereegranskat)abstract
- Collective lattice resonances (CLRs) in finite-sized 2Darrays of dielectric nanospheres have been studied via the coupled dipole approximation. We show that even for sufficiently large arrays, up to 100×100 nanoparticles (NPs),electric or magnetic dipole CLRs may differ significantly from the ones calculated for infinite arrays with the same NP sizes and interparticle distances. The discrepancy is explained by the existence of a sufficiently strong cross-interaction between electric and magnetic dipoles inducedat NPs in finite-sized lattices, which is ignored for infinite arrays. We support this claim numerically and propose an analytic model to estimate a spectral width of CLRs for finite-sized arrays. Given that most of the current theoretical and numerical researches on collective effects in arrays of dielectric NPs rely on modeling infinite structures, there ported findings may contribute to thoughtful and optimal design of inherently finite-sized photonic devices.
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| 10. |
- Zakomirnyi, Vadim I., et al.
(författare)
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Refractory titanium nitride two-dimensional structures with extremely narrow surface lattice resonances at telecommunication wavelengths
- 2017
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Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 111:12
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Tidskriftsartikel (refereegranskat)abstract
- Regular arrays of plasmonic nanoparticles have brought significant attention over the last decade due to their ability to support localized surface plasmons (LSPs) and exhibit diffractive grating behavior simultaneously. For a specific set of parameters (i.e., period, particle shape, size, and material), it is possible to generate super-narrow surface lattice resonances (SLRs) that are caused by interference of the LSP and the grating Rayleigh anomaly. In this letter, we propose plasmonic structures based on regular 2D arrays of TiN nanodisks to generate high-Q SLRs in an important telecommunication range, which is quite difficult to achieve with conventional plasmonic materials. The position of the SLR peak can be tailored within the whole telecommunication bandwidth (from approximate to 1.26 mu m to approximate to 1.62 mu m) by varying the lattice period, while the Q-factor is controlled by changing nanodisk sizes. We show that the Q-factor of SLRs can reach a value of 2 x 10(3), which is the highest reported Q-factor for SLRs at telecommunication wavelengths so far. Tunability of optical properties, refractory behavior, and low-cost fabrication of TiN nanoparticles paves the way for manufacturing cheap nanostructures with extremely stable and adjustable electromagnetic response at telecommunication wavelengths for a large number of applications.
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