Gerd Ulrich Nienhaus | |
---|---|
Nationality | German |
Alma mater | University of Münster |
Scientific career | |
Institutions | Karlsruhe Institute of Technology University of Ulm University of Illinois at Urbana-Champaign University of Mainz University of Münster |
Thesis | Investigation of protein structure and dynamics: x-ray and γ-ray scattering with spatially sensitive proportional counters (translated from German) (1987) |
Website | Nienhaus Group |
Gerd Ulrich "Uli" Nienhaus (born 1959) is a German physicist who is a professor and director of the Institute of Applied Physics, Karlsruhe Institute of Technology (KIT). [1] At the KIT, he is also affiliated with the Institute of Nanotechnology, [2] Institute of Biological and Chemical Systems, [3] and Institute of Physical Chemistry, [4] and he is an adjunct professor at the University of Illinois at Urbana-Champaign. [5]
He is known for his research on the molecular machinery of life. Over the years, he has employed and advanced a wide range of biophysical techniques, including protein crystallography [6] with x-rays and γ-rays, various spectroscopic methods (Mössbauer, XAS, UV-VIS, infrared) and optical fluorescence spectroscopy and microscopy (single-molecule studies, FRET, FLIM, super-resolution microscopy) to elucidate the structure, dynamics and function of biological molecules. He has also been engaged in the development and characterization of nanoscale luminescent markers for bioimaging (fluorescent proteins, gold nanoclusters, semiconductor quantum dots). This research has been documented in more than 500 publications. [7] [8]
Nienhaus studied Physics and Physical Chemistry at the University of Münster, where he received his Diploma in Physics in 1983. [9] In 1988, he earned his PhD in Physical Chemistry with a dissertation entitled (translated from German) "Investigation of protein structure and dynamics: x-ray and γ-ray scattering with spatially sensitive proportional counters". [9] For this research in Fritz Parak's laboratory, he developed large multi-wire proportional counters with spherical drift chambers, [10] which had high long-term stability to enable collection of x-ray and γ-ray crystal diffraction data over many weeks. [11]
After brief postdoctoral stints at the Universities of Münster and Mainz, working on Mössbauer absorption spectroscopy with extremely wide energy windows, [12] Nienhaus moved to the Physics Department of the University of Illinois at Urbana-Champaign in early 1990 as a Feodor Lynen Fellow of the Alexander von Humboldt Foundation. There, he joined the laboratory of Hans Frauenfelder to pursue time-resolved UV-VIS and infrared studies of ligand binding and protein dynamics. [9]
At the University of Illinois, Nienhaus was promoted to research assistant professor (1991), assistant professor of physics (1992) and biophysics (1993) and associate professor with tenure (1996). [13] In this period, his laboratory carried on with studies of ligand binding and protein dynamics, [14] mainly on heme proteins. Since 1997, he has been appointed as an adjunct professor. [5]
In 1996, he accepted an offer to become head and professor of the Department of Biophysics, University of Ulm. There, he continued his research on heme proteins, studying ligand migration within these proteins and its effects on the ligand binding function. [15] He further expanded his portfolio of biophysical methods to include fluorescence correlation spectroscopy and single molecule fluorescence microscopy. [16] In 1999, he took a sabbatical to study RNA dynamics with single molecule FRET in Steve Chu’s laboratory at Stanford University. [17] In Ulm, together with Jörg Wiedenmann, he began to characterize and further develop novel members of the green fluorescent protein family, including EosFP, [18] [19] IrisFP, [20] [21] eqFP611, [22] and mRuby. [23]
In 2009, Nienhaus joined the University of Karlsruhe (TH), which soon thereafter was incorporated into the Karlsruhe Institute of Technology (KIT), as a professor and director of the Institute of Applied Physics. [1] There, he and his collaborators have established a strong research focus on the advancement of optical fluorescence microscopy methods for super-resolution imaging (stimulated emission depletion (STED) nanoscopy, [24] [25] single-molecule localization microscopy) and light-sheet microscopy, and their application to various biological problems. An important research area has been the study of the emission properties of nanoparticles as luminescence markers and their interactions with the biological environment. [26] In collaboration with Andres Jäschke's lab at the University of Heidelberg, single-molecule studies have been performed to study RNA dynamics, [27] and RNA aptamers for super-resolution imaging have been developed and characterized. [28]
Biophysics is an interdisciplinary science that applies approaches and methods traditionally used in physics to study biological phenomena. Biophysics covers all scales of biological organization, from molecular to organismic and populations. Biophysical research shares significant overlap with biochemistry, molecular biology, physical chemistry, physiology, nanotechnology, bioengineering, computational biology, biomechanics, developmental biology and systems biology.
Förster resonance energy transfer (FRET), fluorescence resonance energy transfer, resonance energy transfer (RET) or electronic energy transfer (EET) is a mechanism describing energy transfer between two light-sensitive molecules (chromophores). A donor chromophore, initially in its electronic excited state, may transfer energy to an acceptor chromophore through nonradiative dipole–dipole coupling. The efficiency of this energy transfer is inversely proportional to the sixth power of the distance between donor and acceptor, making FRET extremely sensitive to small changes in distance.
Two-photon excitation microscopy is a fluorescence imaging technique that is particularly well-suited to image scattering living tissue of up to about one millimeter in thickness. Unlike traditional fluorescence microscopy, where the excitation wavelength is shorter than the emission wavelength, two-photon excitation requires simultaneous excitation by two photons with longer wavelength than the emitted light. The laser is focused onto a specific location in the tissue and scanned across the sample to sequentially produce the image. Due to the non-linearity of two-photon excitation, mainly fluorophores in the micrometer-sized focus of the laser beam are excited, which results in the spatial resolution of the image. This contrasts with confocal microscopy, where the spatial resolution is produced by the interaction of excitation focus and the confined detection with a pinhole.
Fluorescence correlation spectroscopy (FCS) is a statistical analysis, via time correlation, of stationary fluctuations of the fluorescence intensity. Its theoretical underpinning originated from L. Onsager's regression hypothesis. The analysis provides kinetic parameters of the physical processes underlying the fluctuations. One of the interesting applications of this is an analysis of the concentration fluctuations of fluorescent particles (molecules) in solution. In this application, the fluorescence emitted from a very tiny space in solution containing a small number of fluorescent particles (molecules) is observed. The fluorescence intensity is fluctuating due to Brownian motion of the particles. In other words, the number of the particles in the sub-space defined by the optical system is randomly changing around the average number. The analysis gives the average number of fluorescent particles and average diffusion time, when the particle is passing through the space. Eventually, both the concentration and size of the particle (molecule) are determined. Both parameters are important in biochemical research, biophysics, and chemistry.
Winfried Denk is a German physicist. He built the first two-photon microscope while he was a graduate student in Watt W. Webb's lab at Cornell University, in 1989.
Single-particle tracking (SPT) is the observation of the motion of individual particles within a medium. The coordinates time series, which can be either in two dimensions (x, y) or in three dimensions (x, y, z), is referred to as a trajectory. The trajectory is typically analyzed using statistical methods to extract information about the underlying dynamics of the particle. These dynamics can reveal information about the type of transport being observed (e.g., thermal or active), the medium where the particle is moving, and interactions with other particles. In the case of random motion, trajectory analysis can be used to measure the diffusion coefficient.
EosFP is a photoactivatable green to red fluorescent protein. Its green fluorescence (516 nm) switches to red (581 nm) upon UV irradiation of ~390 nm due to a photo-induced modification resulting from a break in the peptide backbone near the chromophore. Eos was first discovered as a tetrameric protein in the stony coral Lobophyllia hemprichii. Like other fluorescent proteins, Eos allows for applications such as the tracking of fusion proteins, multicolour labelling and tracking of cell movement. Several variants of Eos have been engineered for use in specific study systems including mEos2, mEos4 and CaMPARI.
Photoactivatable fluorescent proteins (PAFPs) is a type of fluorescent protein that exhibit fluorescence that can be modified by a light-induced chemical reaction.
Graham R. Fleming is a professor of chemistry at the University of California, Berkeley and member of the Kavli Energy NanoScience Institute based at UCB.
Jennifer Lippincott-Schwartz is a Senior Group Leader at Howard Hughes Medical Institute's Janelia Research Campus and a founding member of the Neuronal Cell Biology Program at Janelia. Previously, she was the Chief of the Section on Organelle Biology in the Cell Biology and Metabolism Program, in the Division of Intramural Research in the Eunice Kennedy Shriver National Institute of Child Health and Human Development at the National Institutes of Health from 1993 to 2016. Lippincott-Schwartz received her PhD from Johns Hopkins University, and performed post-doctoral training with Richard Klausner at the NICHD, NIH in Bethesda, Maryland.
Super-resolution microscopy is a series of techniques in optical microscopy that allow such images to have resolutions higher than those imposed by the diffraction limit, which is due to the diffraction of light. Super-resolution imaging techniques rely on the near-field or on the far-field. Among techniques that rely on the latter are those that improve the resolution only modestly beyond the diffraction-limit, such as confocal microscopy with closed pinhole or aided by computational methods such as deconvolution or detector-based pixel reassignment, the 4Pi microscope, and structured-illumination microscopy technologies such as SIM and SMI.
Xiaowei Zhuang is a Chinese-American biophysicist who is the David B. Arnold Jr. Professor of Science, Professor of Chemistry and Chemical Biology, and Professor of Physics at Harvard University, and an Investigator at the Howard Hughes Medical Institute. She is best known for her work in the development of Stochastic Optical Reconstruction Microscopy (STORM), a super-resolution fluorescence microscopy method, and the discoveries of novel cellular structures using STORM. She received a 2019 Breakthrough Prize in Life Sciences for developing super-resolution imaging techniques that get past the diffraction limits of traditional light microscopes, allowing scientists to visualize small structures within living cells. She was elected a Member of the American Philosophical Society in 2019 and was awarded a Vilcek Foundation Prize in Biomedical Science in 2020.
In biophysics and related fields, reduced dimension forms (RDFs) are unique on-off mechanisms for random walks that generate two-state trajectories (see Fig. 1 for an example of a RDF and Fig. 2 for an example of a two-state trajectory). It has been shown that RDFs solve two-state trajectories, since only one RDF can be constructed from the data, where this property does not hold for on-off kinetic schemes, where many kinetic schemes can be constructed from a particular two-state trajectory (even from an ideal on-off trajectory). Two-state time trajectories are very common in measurements in chemistry, physics, and the biophysics of individual molecules (e.g. measurements of protein dynamics and DNA and RNA dynamics, activity of ion channels, enzyme activity, quantum dots ), thus making RDFs an important tool in the analysis of data in these fields.
A two-state trajectory is a dynamical signal that fluctuates between two distinct values: ON and OFF, open and closed, , etc. Mathematically, the signal has, for every either the value or .
Photo-activated localization microscopy and stochastic optical reconstruction microscopy (STORM) are widefield fluorescence microscopy imaging methods that allow obtaining images with a resolution beyond the diffraction limit. The methods were proposed in 2006 in the wake of a general emergence of optical super-resolution microscopy methods, and were featured as Methods of the Year for 2008 by the Nature Methods journal. The development of PALM as a targeted biophysical imaging method was largely prompted by the discovery of new species and the engineering of mutants of fluorescent proteins displaying a controllable photochromism, such as photo-activatible GFP. However, the concomitant development of STORM, sharing the same fundamental principle, originally made use of paired cyanine dyes. One molecule of the pair, when excited near its absorption maximum, serves to reactivate the other molecule to the fluorescent state.
Calcium imaging is a microscopy technique to optically measure the calcium (Ca2+) status of an isolated cell, tissue or medium. Calcium imaging takes advantage of calcium indicators, fluorescent molecules that respond to the binding of Ca2+ ions by fluorescence properties. Two main classes of calcium indicators exist: chemical indicators and genetically encoded calcium indicators (GECI). This technique has allowed studies of calcium signalling in a wide variety of cell types. In neurons, electrical activity is always accompanied by an influx of Ca2+ ions. Thus, calcium imaging can be used to monitor the electrical activity in hundreds of neurons in cell culture or in living animals, which has made it possible to dissect the function of neuronal circuits.
In systems biology, live single-cell imaging is a live cell imaging technique that combines traditional live cell imaging and time-lapse microscopy techniques with automated cell tracking and feature extraction, drawing many techniques from high-content screening. It is used to study signalling dynamics and behaviour in populations of individual living cells. Live single cell studies can reveal key behaviours that would otherwise be masked in population averaging experiments such as western blots.
A genetically engineered fluorescent protein that changes its fluorescence when bound to the neurotransmitter glutamate. Glutamate-sensitive fluorescent reporters are used to monitor the activity of presynaptic terminals by fluorescence microscopy. GluSnFRs are a class of optogenetic sensors used in neuroscience research. In brain tissue, two-photon microscopy is typically used to monitor GluSnFR fluorescence.
FAST is a small, genetically-encoded, protein tag which allows for fluorescence reporting of proteins of interest. Unlike natural fluorescent proteins and derivates such as GFP or mCherry, FAST is not fluorescent by itself. It can bind selectively a fluorogenic chromophore derived from 4-hydroxybenzylidene rhodanine (HBR), which is itself non fluorescent unless bound. Once bound, the pair of molecules goes through a unique fluorogen activation mechanism based on two spectroscopic changes, increase of fluorescence quantum yield and absorption red shift, hence providing high labeling selectivity. The FAST-fluorogen reporting system can be used in fluorescence microscopy, flow cytometry and any other fluorometric method to explore the living world: biosensors, protein trafficking.
Suliana Manley is an American biophysicist. Her research focuses on the development of high-resolution optical instruments, and their application in studying the organization and dynamics of proteins. She is a professor at École Polytechnique Fédérale de Lausanne and heads the Laboratory of Experimental Biophysics.