Browsing by Subject "fluorescence microscopy"

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  • Allolio, Christoph; Magarkar, Aniket; Jurkiewicz, Piotr; Baxova, Katarina; Javanainen, Matti; Mason, Philip E.; Sachl, Radek; Cebecauer, Marek; Hof, Martin; Horinek, Dominik; Heinz, Veronika; Rachel, Reinhard; Ziegler, Christine M.; Schröfel, Adam; Jungwirth, Pavel (2018)
    Arginine-rich cell-penetrating peptides do not enter cells by directly passing through a lipid membrane; they instead passively enter vesicles and live cells by inducing membrane multilamellarity and fusion. The molecular picture of this penetration mode, which differs qualitatively from the previously proposed direct mechanism, is provided by molecular dynamics simulations. The kinetics of vesicle agglomeration and fusion by an iconic cell-penetrating peptide-nonaarginine-are documented via real-time fluorescence techniques, while the induction of multilamellar phases in vesicles and live cells is demonstrated by a combination of electron and fluorescence microscopies. This concert of experiments and simulations reveals that the identified passive cell penetration mechanism bears analogy to vesicle fusion induced by calcium ions, indicating that the two processes may share a common mechanistic origin.
  • Salmi, Pauliina; Mäki, Anita; Mikkonen, Anu; Pupponen, Veli-Mikko; Vuorio, Kristiina; Tiirola, Marja (Suomen ympäristökeskus, 2021)
    Boreal Environment Research 26: 17-27
    The smaller the phytoplankton, the greater effort is required to distinguish individual cells by optics-based methods. Flow cytometry is widely applied in marine picophytoplankton research, but in freshwater research its role has remained minor. We compared epifluorescence microscopy and flow cytometry in assessing the composition, abundance and cell sizes of autofluorescent picophytoplankton in epilimnia of 46 Finnish lakes. Phycocyaninrich picocyanobacteria were the most dominant. The two methods yielded comparable total picophytoplankton abundances, but the determination of cell sizes, and thus total biomasses, were on average an order of magnitude higher in the microscopy results. However, flow cytometry yielded higher cell sizes when applied on small-celled cultured algae. Our study demonstrated that both epifluorescence microscopy and flow cytometry are useful methods in assessing abundances of phycocyanin-rich and phycoerythrin-rich picocyanobacteria and eukaryotic picophytoplankton in lakes. However, accurate determination of cell size and biomass remain challenges for microscopy and especially for flow cytometry.
  • Kiurusalmi, Mirja K. (Helsingin yliopisto, 2015)
    Beta-glucan ((1-3),(1-4)-?-D-glucan) is a soluble cell wall polysachharide in the starchy endosperm and aleurone layer of cereal grains. It is able to form the viscose solution at low concentrations and it can form gels under certain conditions. The literature review focused on physicochemical properties of beta-glucan. Especially gelling properties and influencing contributors for gelling were discussed. Aim of the experimental studies was to study effects of different solubilization temperatures on solution properties of barley beta-glucan. Furthermore, alteration on structuring properties of beta-glucan during the storage was observed. The study explored how beta-glucan behaves in water solution and does it has a gelling properties at low concentration. In this study pure barley beta-glucan (Megazyme, 99,5 %) (concentration 1 % v/w) was solubilized in water at three different temperatures (37, 60 ja 85 °C). Samples were stored at room temperature (+21 °C) and in the cold (+5 °C) for one week. Viscoelastic properties of the samples were measured by the dynamic rhelogical measurement with two different probes. Samples were treated with calcofluor-reagent and imaged by fluorescencemicroscopy. Furthemore, photographs were taken in three or four different dates during the storage time. Structure forming and gelling properties of pure barley beta-glucan differed among the samples when different solubilization temperatures were used. The pure barley beta-glucan was partly solubilized and formed opaque and smooth gel-like structure when 60 °C solubilizing temperature were used. Fluorescence microscopy showed that many unsolubilized particles were remained in both room and cold stored 60 °C samples. Unsolubilized particles formed rapidly continuous network structures during storage, especially in cold stored sample. Both 60 °C samples showed viscoelastic behavior and had weak gel properties which were observed by dynamic rheological measurement. Sample which was solubilized at 37 °C had part of structures gel-like after storage. Large unsolubilized particles were observed in 37 °C sample after solubilization which was also revealed by fluorescence microscopy. Sample which was solubilized at 85 °C was well-dissolved and formed clear solution. In 85 °C sample were few and small particles and gel-like structure did not formed during storage. However, formation of particle clusters was observed by fluorescence microscopy in all samples with particle sizes and structures increasing after storage one week. The results of this study indicated that solubilization and storage temperatures effected on forming particles and structures of pure barley beta-glucan during storage. This study showed that solubilization temperature effected on gelling properties of pure barley beta-glucan at low concetration.