| 1. |
- Malyshev, Dmitry, et al.
(författare)
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Laser induced degradation of bacterial spores during micro-Raman spectroscopy
- 2022
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Ingår i: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - : Elsevier. - 1386-1425 .- 1873-3557. ; 265
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Tidskriftsartikel (refereegranskat)abstract
- Micro-Raman spectroscopy combined with optical tweezers is a powerful method to analyze how the biochemical composition and molecular structures of individual biological objects change with time. In this work we investigate laser induced effects in the trapped object. Bacillus thuringiensis spores, which are robust organisms known for their resilience to light, heat, and chemicals are used for this study. We trap spores and monitor the Raman peak from CaDPA (calcium dipicolinic acid), which is a chemical protecting the spore core. We see a correlation between the amount of laser power used in the trap and the release of CaDPA from the spore. At a laser power of 5 mW, the CaDPA from spores in water suspension remain intact over the 90 min experiment, however, at higher laser powers an induced effect could be observed. SEM images of laser exposed spores (after loss of CaDPA Raman peak was confirmed) show a notable alteration of the spores' structure. Our Raman data indicates that the median dose exposure to lose the CaDPA peak was ∼60 J at 808 nm. For decontaminated/deactivated spores, i.e., treated in sodium hypochlorite or peracetic acid solutions, the sensitivity on laser power is even more pronounced and different behavior could be observed on spores treated by the two chemicals. Importantly, the observed effect is most likely photochemical since the increase of the spore temperature is in the order of 0.1 K as suggested by our numerical multiphysics model. Our results show that care must be taken when using micro-Raman spectroscopy on biological objects since photoinduced effects may substantially affect the results.
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| 2. |
- Malyshev, Dmitry, et al.
(författare)
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pH induced changes in Raman, UV-Vis absorbance, and fluorescence spectra of dipicolinic acid (DPA)
- 2022
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Ingår i: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - : Elsevier. - 1386-1425 .- 1873-3557. ; 271
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Tidskriftsartikel (refereegranskat)abstract
- Dipicolinic acid (DPA) is an essential component for the protection of DNA in bacterial endospores and is often used as a biomarker for spore detection. Depending upon the pH of the solution, DPA exists in different ionic forms. Therefore, it is important to understand how these ionic forms influence spectroscopic response. In this work, we characterize Raman and absorption spectra of DPA in a pH range of 2.0–10.5. We show that the ring breathing mode Raman peak of DPA shifts from 1003 cm−1 to 1017 cm−1 and then to 1000 cm−1 as pH increases from 2 to 5. The relative peak intensities related to the different ionic forms of DPA are used to experimentally derive the pKa values (2.3 and 4.8). We observe using UV–vis spectroscopy that the changes in the absorption spectrum of DPA as a function of pH correlate with the changes observed in Raman spectroscopy, and the same pKa values are verified. Lastly, using fluorescence spectroscopy and exciting a DPA solution at between 210–330 nm, we observe a shift in fluorescence emission from 375 nm to 425 nm between pH 2 and pH 6 when exciting at 320 nm. Our work shows that the different spectral responses from the three ionic forms of DPA may have to be taken into account in, e.g., spectral analysis and for detection applications.
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| 3. |
- Öberg, Rasmus, et al.
(författare)
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Characterization of carfentanil and thiofentanil using surface-enhanced raman spectroscopy and density functional theory
- 2024
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Ingår i: Journal of Raman Spectroscopy. - : John Wiley & Sons. - 0377-0486 .- 1097-4555. ; 55:4, s. 481-492
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Tidskriftsartikel (refereegranskat)abstract
- Fentanyls are synthetic opioids up to 10,000 times more potent than morphine. Although initially developed for medical applications, fentanyl and its analogues have recently grown synonymous with the ongoing opioid epidemic. To combat the continued spread of these substances, there is a need for rapid and sensitive techniques for chemical detection. Surface-enhanced Raman spectroscopy (SERS) has the potential for trace detection of harmful chemical substances. However, vibrational spectra obtained by SERS often differ between SERS substrates, as well as compared with spectra from normal Raman (NR) spectroscopy. Herein, SERS and NR responses from two fentanyl analogues, carfentanil (CF) and thiofentanil (TF), were measured and analysed with support from density functional theory (DFT) modelling. Using commercially available silver nanopillar SERS substrates, the SERS signatures of samples diluted in acetonitrile between 0.01 and 1000 µg/mL were studied. Relative SERS peak intensities measured in the range of 220–1800 cm−1 vary with concentration, while SERS and NR spectra largely agree for CF at higher concentrations ((Formula presented.) 100 µg/mL). For TF, three distinct NR peaks at 262, 366 and 667 cm−1 are absent or strongly suppressed in the SERS spectrum, attributed to the lone-pair electrons of the thiophene's sulphur atom binding to the Ag surface. The concentration dependence of the Raman peak at (Formula presented.) 1000 cm−1, assigned to trigonal bending of the phenyl ring, approximately follows a Langmuir adsorption isotherm. This work elucidates similarities and differences between SERS and NR in fentanyl detection and discusses the chemical rationale behind these differences.
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| 4. |
- Öberg, Rasmus, et al.
(författare)
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UV-induced spectral and morphological changes in bacterial spores for inactivation assessment
- 2024
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 128:7, s. 1638-1646
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Tidskriftsartikel (refereegranskat)abstract
- The ability to detect and inactivate spore-forming bacteria is of significance within, for example, industrial, healthcare, and defense sectors. Not only are stringent protocols necessary for the inactivation of spores but robust procedures are also required to detect viable spores after an inactivation assay to evaluate the procedure’s success. UV radiation is a standard procedure to inactivate spores. However, there is limited understanding regarding its impact on spores’ spectral and morphological characteristics. A further insight into these UV-induced changes can significantly improve the design of spore decontamination procedures and verification assays. This work investigates the spectral and morphological changes to Bacillus thuringiensis spores after UV exposure. Using absorbance and fluorescence spectroscopy, we observe an exponential decay in the spectral intensity of amino acids and protein structures, as well as a logistic increase in dimerized DPA with increased UV exposure on bulk spore suspensions. Additionally, using micro-Raman spectroscopy, we observe DPA release and protein degradation with increased UV exposure. More specifically, the protein backbone’s 1600–1700 cm–1 amide I band decays slower than other amino acid-based structures. Last, using electron microscopy and light scattering measurements, we observe shriveling of the spore bodies with increased UV radiation, alongside the leaking of core content and disruption of proteinaceous coat and exosporium layers. Overall, this work utilized spectroscopy and electron microscopy techniques to gain new understanding of UV-induced spore inactivation relating to spore degradation and CaDPA release. The study also identified spectroscopic indicators that can be used to determine spore viability after inactivation. These findings have practical applications in the development of new spore decontamination and inactivation validation methods.
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| 5. |
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| 6. |
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| 7. |
- Andersson, Kent, 1967-, et al.
(författare)
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Introduktion till Operationsanalys : En antologi med essäer av studerande i militärteknik 2011
- 2012
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- I ämnesplanen definieras militärteknik som ”den vetenskap som beskriver och förklarar hur tekniken inverkar på militär verksamhet på alla nivåer, strategisk, operativ och taktisk, samt hur officersprofessionen påverkar och påverkas av tekniken.”[1] En militärteknikers uppgift brukar, utgående från definitionen, uttryckas som att beskriva och förklara den militära nyttan med tekniken. För att kunna göra detta behövs verktyg. Och många av dem kommer från den vetenskapliga disciplinen Operationsanalys.Syftet med den här antologin är att introducera studerande i militärteknik på Försvarshögskolan till två av de mest refererade boktitlarna i operationsanalys – Methods for conducting military operational analysis editerad av Andrew G. Loerch och Larry B. Rainey samt Military Operations Research, quantitative decision making av N.K. Jaiswal.Kapitlen utgörs av essäer skrivna av studerande på den högre stabsofficersutbildningen med teknisk inriktning, som examinationsuppgift i en fördjupningskurs. Essäerna är till del referat av kapitel i de två böckerna ovan, men kryddade med exempel satta i svenskt sammanhang och med de studerandes egen värdering av metodernas användbarhet.[1]Försvarshögskolan, Ämnesplan militärteknik, 2007.
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| 8. |
- Andersson, Mats, et al.
(författare)
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Laser spectroscopy of gas in scattering media at scales ranging from kilometers to millimeters
- 2007
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Ingår i: Laser Physics. - 1054-660X. ; 17:7, s. 893-902
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Tidskriftsartikel (refereegranskat)abstract
- Free gases are characterized by their narrow line width, and they can conveniently be studied by laser spectroscopy. The present paper discusses the monitoring of such ambient pressure gases, which are dispersed in scattering media such as aerosol-laden atmospheres, solids, or liquids. Atmospheric work basically constitutes the well-known field of differential absorption lidar (DIAL), while the study of free gas in solids and liquids was initiated more recently under the name of GASMAS (GAs in Scattering Media Absorption Spectroscopy). We discuss the connections between the two techniques, which are extensively used in our labortory. Thus, we span the field from trace-gas mapping of gases in the lower atmosphere to gas studies in construction materials, food products, and the human body. We show that the basic ideas are very similar, while the spatial and temporal scales vary greatly.
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| 9. |
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| 10. |
- Andersson, Rasmus, 1990, et al.
(författare)
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CHAMPION: Chalmers hierarchical atomic, molecular, polymeric and ionic analysis toolkit
- 2021
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Ingår i: Journal of Computational Chemistry. - : Wiley. - 0192-8651 .- 1096-987X. ; 42:23, s. 1632-1642
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Tidskriftsartikel (refereegranskat)abstract
- We present CHAMPION (Chalmers hierarchical atomic, molecular, polymeric, and ionic analysis toolkit): a software developed to automatically detect time-dependent bonds between atoms based on their dynamics, classify the local graph topology around them, and analyze the physicochemical properties of these topologies by statistical physics. In stark contrast to methodologies where bonds are detected based on static conditions such as cut-off distances, CHAMPION considers pairs of atoms to be bound only if they move together and act as a bound pair over time. Furthermore, the time-dependent global bond graph is possible to split into dynamically shifting connected components or subgraphs around a certain chemical motif and thereby allow the physicochemical properties of each such topology to be analyzed by statistical physics. Applicable to condensed matter and liquids in general, and electrolytes in particular, this allows both quantitative and qualitative descriptions of local structure, as well as dynamical processes such as speciation and diffusion. We present here a detailed overview of CHAMPION, including its underlying methodology, implementation, and capabilities.
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