Vladimir N. Belov

Bio: Vladimir N. Belov is an academic researcher from Max Planck Society. The author has contributed to research in topics: STED microscopy & Fluorescence. The author has an hindex of 35, co-authored 119 publications receiving 5622 citations. Previous affiliations of Vladimir N. Belov include University of Göttingen & Saint Petersburg State University.

Direct observation of the nanoscale dynamics of membrane lipids in a living cell

Abstract: Cholesterol-mediated lipid interactions are thought to have a functional role in many membrane-associated processes such as signalling events. Although several experiments indicate their existence, lipid nanodomains ('rafts') remain controversial owing to the lack of suitable detection techniques in living cells. The controversy is reflected in their putative size of 5-200 nm, spanning the range between the extent of a protein complex and the resolution limit of optical microscopy. Here we demonstrate the ability of stimulated emission depletion (STED) far-field fluorescence nanoscopy to detect single diffusing (lipid) molecules in nanosized areas in the plasma membrane of living cells. Tuning of the probed area to spot sizes approximately 70-fold below the diffraction barrier reveals that unlike phosphoglycerolipids, sphingolipids and glycosylphosphatidylinositol-anchored proteins are transiently ( approximately 10-20 ms) trapped in cholesterol-mediated molecular complexes dwelling within <20-nm diameter areas. The non-invasive optical recording of molecular time traces and fluctuation data in tunable nanoscale domains is a powerful new approach to study the dynamics of biomolecules in living cells.

Photochromic rhodamines provide nanoscopy with optical sectioning

Abstract: Since the seminal work of Abbe in 1873, it has been commonly assumed that the resolution of a lens-based (farfield) light microscope is limited to about half the wavelength of the light used ( l/2). However, in the mid-1990s, fluorescence microscopy concepts emerged that demonstrated that the limiting role of diffraction could be fundamentally overcome. The main hallmark of these concepts was to use the states of the fluorescent marker not just for generating the signal, but also for breaking the diffraction barrier. In fact, all the methods that have successfully outperformed diffraction have so far relied on selected pairs of molecular states—specifically, a “bright” one to generate the signal and a “dark” one to ensure that the measured signal stems from a subdiffraction-sized region. For example, stimulated emission depletion microscopy relies on the quenching of the fluorescent singlet state to the (dark) ground state by using a focal intensity distribution featuring a zero. Thus, all molecules are “switched off” except those located at the position of the zero. This concept has been successfully extended to switching between (metastable) states of fluorescent proteins 4] and photochromic organic compounds. In this case, the switching occurs between (conformational) states, in one of which the molecule is able to successively emit fluorescence photons. The benefit is that the switching can be performed at low levels of light. An alternative way of using molecular photoswitching to break the diffraction barrier is to stochastically switch on, read out the fluorescence, and switch off isolated marker molecules such that simultaneously emitting (“on”) markers are further apart than the minimal distance resolved by the microscope. In this case, the spatial confinement of the fluorescence is down to the size of a single molecule by definition. Imaging the fluorescence signal from an individual marker onto a camera produces a diffraction spot whose centroid yields the location of the emitter, with a precision that ideally depends just on the number of collected photons n and on the full-width-half-maximum (FWHM) of the fluorescence spot, and is approximately given by FWHM/ ffiffiffi

Multicolor Far-Field Fluorescence Nanoscopy through Isolated Detection of Distinct Molecular Species

Abstract: By combining the photoswitching and localization of individual fluorophores with spectroscopy on the single molecule level, we demonstrate simultaneous multicolor imaging with low crosstalk and down to 15 nm spatial resolution using only two detection color channels. The applicability of the method to biological specimens is demonstrated on mammalian cells. The combination of far-field fluorescence nanoscopy with the recording of a single switchable molecular species at a time opens up a new class of functional imaging techniques.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Lipid Rafts As a Membrane-Organizing Principle

Abstract: Cell membranes display a tremendous complexity of lipids and proteins designed to perform the functions cells require. To coordinate these functions, the membrane is able to laterally segregate its constituents. This capability is based on dynamic liquid-liquid immiscibility and underlies the raft concept of membrane subcompartmentalization. Lipid rafts are fluctuating nanoscale assemblies of sphingolipid, cholesterol, and proteins that can be stabilized to coalesce, forming platforms that function in membrane signaling and trafficking. Here we review the evidence for how this principle combines the potential for sphingolipid-cholesterol self-assembly with protein specificity to selectively focus membrane bioactivity.

Photochromism of Diarylethene Molecules and Crystals: Memories, Switches, and Actuators

Abstract: Switches, and Actuators Masahiro Irie,*,† Tuyoshi Fukaminato,‡ Kenji Matsuda, and Seiya Kobatake †Research Center for Smart Molecules, Rikkyo University, Nishi-Ikebukuro 3-34-1, Toshima-ku, Tokyo 171-8501, Japan ‡Research Institute for Electronic Science, Hokkaido University, N20, W10, Kita-ku, Sapporo 001-0020, Japan Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan Department of Applied Chemistry, Graduate School of Engineering, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan

Super-Resolution Fluorescence Microscopy

Abstract: Achieving a spatial resolution that is not limited by the diffraction of light, recent developments of super-resolution fluorescence microscopy techniques allow the observation of many biological structures not resolvable in conventional fluorescence microscopy. New advances in these techniques now give them the ability to image three-dimensional (3D) structures, measure interactions by multicolor colocalization, and record dynamic processes in living cells at the nanometer scale. It is anticipated that super-resolution fluorescence microscopy will become a widely used tool for cell and tissue imaging to provide previously unobserved details of biological structures and processes.