Stefan Wennmalm

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The mechanisms controlling the conversion of spider silk proteins into insoluble fibres, which happens in a fraction of a second and in a defined region of the silk glands, are still unresolved. The N-terminal domain changes conformation and forms a homodimer when pH is lowered from 7 to 6; however, the molecular details still remain to be determined. Here(More)
We have built a fluorescence correlation spectroscopy (FCS) microscope for ultraviolet excitation (280-300 nm) and emission. With UV excitation the fluorescence of 'natural fluorophores' such as the modified nucleotide 2-aminopurine can be analyzed. The sensitivity of a natural fluorophore toward conformational changes can reveal dynamics in biomolecules.(More)
We describe here the enzyme-catalyzed, low-density labeling of DNAs with fluorescent dyes. Firstly, for "natural" template DNAs, dNTPs were partially substituted in the labeling reactions by the respective fluorophore-bearing analogs. The DNAs were labeled by PCR using Taq DNA polymerase. The covalent incorporation of dye-dNTPs decreased in the following(More)
Studying the properties of individual events and molecules offers a host of advantages over taking only macroscopic measurements of populations. Here we review such advantages, as well as some pitfalls, focusing on examples from biological imaging. Examples include single proteins, their interactions in cells, organelles, and their interactions both with(More)
An alternative version of fluorescence correlation spectroscopy is presented, where the signal from a medium surrounding the particles of interest is analyzed, as opposed to a signal from the particles themselves. This allows for analysis of unlabeled particles and potentially of biomolecules. Here, the concept together with principal experiments on(More)
Measurement of fluorescent lifetimes of dye-tagged DNA molecules reveal the existence of different conformations. Conformational fluctuations observed by fluorescence correlation spectroscopy give rise to a relaxation behavior that is described by "stretched" exponentials and indicates the presence of a distribution of transition rates between two(More)
Inverse-fluorescence correlation spectroscopy (iFCS) was recently introduced as an alternative version of FCS that does not require labeling of the analyzed particles or biomolecules. In iFCS, the signal from a medium surrounding the particles is analyzed, as opposed to a signal from the studied particles themselves. As unlabeled particles diffuse through(More)
A novel fluctuation spectroscopy technique based on interferometry is described. The technique, termed scattering interference correlation spectroscopy (SICS), autocorrelates the signals from the forward-scattered and transmitted laser light from nanoparticles (NPs) in solution. SICS has two important features: First, for unlabeled NPs with known refractive(More)
Oligomers formed by the amyloid β-peptide (Aβ) are pathogens in Alzheimer's disease. Increased knowledge on the oligomerization process is crucial for understanding the disease and for finding treatments. Ideally, Aβ oligomerization should be studied in solution and at physiologically relevant concentrations, but most popular techniques of today are not(More)
Elevated basal insulin secretion under fasting conditions together with insufficient stimulated insulin release is an important hallmark of type 2 diabetes, but the mechanisms controlling basal insulin secretion remain unclear. Membrane rafts exist in pancreatic islet cells and spatially organize membrane ion channels and proteins controlling exocytosis,(More)