| 1. |
|
|
| 2. |
- Adams, Kelly L., et al.
(författare)
-
Steady-State Electrochemical Determination of Lipidic Nanotube Diameter Utilizing an Artificial Cell Model
- 2010
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 82:3, s. 1020-1026
-
Tidskriftsartikel (refereegranskat)abstract
- By exploiting the capabilities of steady-state electrochemical measurements, we have measured the inner diameter of a lipid nanotube using Fick’s first law of diffusion in conjunction with an imposed linear concentration gradient of electroactive molecules over the length of the nanotube. Fick’s law has been used in this way to provide a direct relationship between the nanotube diameter and the measurable experimental parameters Δi (change in current) and nanotube length. Catechol was used to determine the Δi attributed to its flux out of the nanotube. Comparing the nanotube diameter as a function of nanotube length revealed that membrane elastic energy was playing an important role in determining the size of the nanotube and was different when the tube was connected to either end of two vesicles or to a vesicle on one end and a pipet tip on the other. We assume that repulsive interaction between neck regions can be used to explain the trends observed. This theoretical approach based on elastic energy considerations provides a qualitative description consistent with experimental data.
|
|
| 3. |
- Cheregi, Otilia, et al.
(författare)
-
Transcriptome analysis reveals insights into adaptive responses of two marine microalgae species to Nordic seasons
- 2023
-
Ingår i: Algal Research. - 2211-9264. ; 74
-
Tidskriftsartikel (refereegranskat)abstract
- There is an increasing interest in algae-based biomass produced outdoors in natural and industrial settings for biotechnological applications. To predict the yield and biochemical composition of the biomass, it is important to understand how the transcriptome of species and strains of interest is affected by seasonal changes. Here we studied the effects of Nordic winter and summer on the transcriptome of two phytoplankton species, namely the diatom Skeletonema marinoi (Sm) and the eustigmatophyte Nannochloropsis granulata (Ng), recently identified as potentially important for biomass production on the west coast of Sweden. Cultures were grown in photobioreactors in simulated Nordic summer and winter, and the gene expression in two phases was quantified by Illumina RNA-sequencing. Five paired comparisons were made among the four conditions. Sm was overall more responsive to seasons since 70 % of the total transcriptome (14,783 genes) showed differential expression in at least one comparison as compared to 1.6 % (1403 genes) for Ng. For both species, we observed larger differences between the seasons than between the phases of the same season. In summer phase 1, Sm cells focused on photosynthesis and polysaccharide biosynthesis. Nitrate assimilation and recycling of intracellular nitrogen for protein biosynthesis were more active in summer phase 2 and throughout winter. Lipid catabolism was upregulated in winter relative to summer to supply carbon for respiration. Ng favored lipid accumulation in summer, while in winter activated different lipid remodeling pathways as compared to Sm. To cope with winter, Ng upregulated breakdown and transport of carbohydrates for energy production. Taken together, our transcriptome data reveal insights into adaptive seasonal responses of Sm and Ng important for biotechnological applications on the west coast of Sweden, but more work is required to decipher the molecular mechanisms behind these responses.
|
|
| 4. |
- Ekendahl, Susanne, 1965, et al.
(författare)
-
Energieffektiv odling av marina mikroalger vid den svenska västkusten - potentiella applikationer : RISE Rapport 2020: 72
- 2020
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- An energy-efficient cultivation method for microalgae has been further developed for the Nordic climate, specifically for the Swedish west coast. The principle for the cultivation process has earlier been developed by RISE for freshwater microalgae. In this project, we have used marine species, and thereby also seawater, in the cultivation. Utilization of natural seawater lowers the environmental impact since, during some circumstances, freshwater may become limiting even in Sweden. The aim of the study was to investigate if selected marine species could be rotated during the year to achieve a longer cultivation season and increased production of energy-rich algal biomass. Winter, spring and summer at the Swedish west coast were simulated in cultivation experiments in laboratory bioreactors with the species Skeletonema marinoi, usually thriving and blooming on the west coast in winter and spring, and Nannochloropsis granulata, which blooms in summer and produces high amounts of lipids. Nannochloropsis was shown to be more suitable for cultivation during spring and summer, when it comes to production of biomass and energy, while Skeletonema grew better during winter and displayed a higher uptake of phosphate than Nannochloropsis. The productivity of Nannochloropsis was in the same range as that of a previously studied freshwater microalgal species, Tetradesmus obliquus. We have shown the principle for a rotational cultivation strategy and that species adapted for a cold climate can give higher productivity during the cold season. Nevertheless, the selected species (Skeletonema) generally showed too low productivity when cultivated during winter to be energy efficient. More species need to be studied to identify those with a high productivity during winter conditions. Even if cold-adapted species are less productive than the summer-adapted ones, considering the available sunlight, they could still be used to prolong the growth season. The cultivation process of Nannochloropsis could also be optimized in an outdoor environment to prolong the season in different ways, since it was tolerant to cold conditions. In practice, the work-related consequences of a rotational cultivation should be weighed against its benefits for each application. Possible applications mainly include cleaning of air and seawater, production of energy, biomass and biomaterials for the industry.
|
|
| 5. |
- Eliasson, Charlotte, 1973, et al.
(författare)
-
Multivariate methodology for surface enhanced Raman chemical imaging of lymphocytes
- 2006
-
Ingår i: Chemometrics and Intelligent Laboratory Systems. - : Elsevier BV. - 0169-7439 .- 1873-3239. ; 81:1, s. 13-20
-
Tidskriftsartikel (refereegranskat)abstract
- Surface enhanced Raman spectroscopy (SERS) was used to study the uptake of rhodamine 6G in human lymphocytes. In total four Raman images of lymphocytes were used. The aim was to find a multivariate methodology capable of separating spectra with chemical information from those that mainly contained the surface enhanced background, in order to create chemical images. The standard PCA procedure was compared with PCA of standard normal variate (SNV) corrected spectra, spectra baseline corrected in the wavelet domain, and variable trimming before PCA, to isolate unique spectra. It was not straightforward to perform a standard PCA for overview, since the small background variation in many variables dominated over the Raman band variation that only occur in few variables. It was shown that wavelet filtering could remove background variations and that variable trimming followed by PCA modelling left the unique Raman spectra as outliers, which facilitated interpretation of the Raman score images.
|
|
| 6. |
- Eliasson, Charlotte, 1973, et al.
(författare)
-
Surface-enhanced Raman scattering imaging of single living lymphocytes with multivariate evaluation
- 2005
-
Ingår i: Spectrochimica Acta Part A-Molecular and Biomolecular Spectroscopy. - : Elsevier BV. - 1386-1425. ; 61:4, s. 755-760
-
Tidskriftsartikel (refereegranskat)abstract
- This paper is aimed to show the possibility to determine individual organic compounds introduced into single living cells with surface-enhanced Raman spectroscopy (SERS). Surface enhancement was achieved with gold colloids that were allowed to diffuse into lymphocytes. An introduced analyte, rhodamine 6G, could be imaged together with for example nucleotides and amino acids of the cell. Multivariate evaluation of surface-enhanced Raman images proved to be a powerful tool for the separation of spectral information of various intracellular components. The principal component analysis (PCA) enabled identification of spectra containing different chemical information and separation of the spectral contribution of rhodamine 6G from the complex cellular matrix.
|
|
| 7. |
|
|
| 8. |
- Engelbrektsson, Johan, 1976
(författare)
-
Multivariate Measurements and Chemical Imaging of Organic Compounds
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chemical imaging is an emerging analytical technique, based on the interplay between, most often, spectroscopic measurements and advanced evaluation methodology. With this we can study the distribution of chemical compounds in different compartments, such as individual cells and pharmaceutical tablets. Also, chemical imaging allows for studies of time dependent processes, such as uptake of drugs or dissolution.Surface enhanced Raman spectroscopy (SERS) was used to acquire data in complex matrices (lymphocytes), the spectra obtained varied significantly in background and intensity. Near-infrared spectroscopy (NIR) and atomic force microscopy (AFM) were used to characterise the texture of pharmaceutical tablets. Also, the dissolution of a tablet was monitored over time.The focus of this thesis is the data analysis, more specifically the multivariate handling of large data sets, comparisons of images, structure identification and textures. Three application areas have been more thoroughly investigated; normalisation of spectral data to obtain quantitative results during difficult statistical sampling conditions; extraction of relevant spectral and chemical information from complex matrices and measurements in noisy or high-background environments; detection of small changes in spatial features. A normalisation method for highly variable SERS measurements, based on an internal standard self assembled monolayer was developed and studied for use with multivariate regression. It was shown that the highly variable background in SERS imaging could be reduced with wavelet filtering and modelling of the background to extract chemically interesting spectra as outliers. Together with the concept of an internal standard applied as a self assembled monolayer, this points in the direction of a solution for quantitative SERS.The use of wavelet transformation in combination with principal components analysis, were shown to be successful in characterisation of spatial features without prior segmentation. Continuous wavelet transform (CWT) gave more consistent results in texture analysis than discrete wavelet transform (DWT), and dual-tree complex wavelet transform (DT-CWT).
|
|
| 9. |
- Hakonen, Aron, 1970, et al.
(författare)
-
A potential tool for high-resolution monitoring of ocean acidification.
- 2013
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 786, s. 1-7
-
Tidskriftsartikel (refereegranskat)abstract
- Current anthropogenic carbon dioxide emissions generate besides global warming unprecedented acid-ification rates of the oceans. Recent evidence indicates the possibility that ocean acidification and lowoceanic pH may be a major reason for several mass extinctions in the past. However, a major bottleneck forresearch on ocean acidification is long-term monitoring and the collection of consistent high-resolutionpH measurements. This study presents a low-power (<1 W) small sample volume (25l) semiconductor based fluorescence method for real-time ship-board pH measurements at high temporal and spatialresolution (approximately 15 s and 100 m between samples). A 405 nm light emitting diode and the blueand green channels from a digital camera was used for swift detection of fluorescence from the pH sen-sitive dye 6,8-Dihydroxypyrene-1,3-disulfonic acid in real-time. Main principles were demonstrated byautomated continuous measurements of pH in the surface water across the Baltic Sea and the Kattegatregion with a large range in salinity (∼3–30) and temperature (∼0–25◦C). Ship-board precision of salinityand temperature adjusted pH measurements were estimated as low as 0.0001 pH units.
|
|
| 10. |
- Kuklinski, Nicholas J., et al.
(författare)
-
Biogenic Amines in Microdissected Brain Regions of Drosophila melanogaster Measured with Mice liar Electrokinetic Capillary Chromatography-Electrochemical Detection
- 2010
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 82:18, s. 7729-7735
-
Tidskriftsartikel (refereegranskat)abstract
- Micellar electrokinetic chromatography with electrochemical detection has been used to quantify biogenic amines in microdissected Drosophila melanogaster brains and brain regions. The effects of pigment from the relatively large fly eyes on the separation have been examined to find that the red pigment from the compound eye masks much of the signal from biogenic amines. The brains of white mutant flies, which have characteristically low pigment in the eyes, have a significantly simplified separation profile in comparison to the red-eyed, wild-type, Canton S fly. Yet, the white mutant flies were found to have significantly less amounts of dopamine, I-3,4-dihydroxyphenylalanine (L-DOPA), salsolinol, and N-acetyltyramine in their dissected brains when compared to dissected brains of Canton S flies. In addition, significant variation has been observed in the dissected brains between individual flies that might be related to changes in neurotransmitter turnover. The transgenic GFP fly line (TH-GFP), for which the overall profile of biogenic amines is not found to be significantly different from Canton S, can be used to visualize the location of dopamine neurons. Biogenic amines were then quantified in three brain regions observed to have dopamine levels, the central brain, optic lobes, and posterior superiormedial proto-cerebrum (PPM1) region.
|
|
