Consensus Statement on Brillouin Light Scattering Microscopy of Biological Materials.

Brillouin Light Scattering (BLS) spectroscopy is a non-invasive, non-contact, label-free optical technique that can provide information on the mechanical properties of a material on the sub-micron scale. Over the last decade it has seen increased applications in the life sciences, driven by the observed significance of mechanical properties in biological processes, the realization of more sensitive BLS spectrometers and its extension to an imaging modality. As with other spectroscopic techniques, BLS measurements not only detect signals characteristic of the investigated sample, but also of the experimental apparatus, and can be significantly affected by measurement conditions.

The tyrosine kinase inhibitor Nintedanib induces lysosomal dysfunctionality: Role of protonation-dependent crystallization processes.

Nintedanib (NIN), a multi-tyrosine kinase inhibitor clinically approved for idiopathic pulmonary fibrosis and lung cancer, is characterized by protonation-dependent lysosomotropic behavior and appearance of lysosome-specific fluorescence emission properties. Here we investigate whether spontaneous formation of a so far unknown NIN matter within the acidic cell compartment is underlying these unexpected emissive properties and investigate the consequences on lysosome functionality. Lysosomes of cells treated with NIN, but not non-protonatable NIN derivatives, exhibited lysosome-associated birefringence signals co-localizing with the NIN-derived fluorescence emission.

Diagnostic potential of blood plasma longitudinal viscosity measured using Brillouin light scattering.

Blood plasma viscosity (PV) is an established biomarker for numerous diseases. Measurement of the shear PV using conventional rheological techniques is, however, time consuming and requires significant plasma volumes. Here, we show that Brillouin light scattering (BLS) and angle-resolved spectroscopy measurements of the longitudinal PV from microliter-sized plasma volumes can serve as a proxy for the shear PV measured using conventional viscometers.

Hormone-regulated expansins: Expression, localization, and cell wall biomechanics in Arabidopsis root growth.

Expansins facilitate cell expansion by mediating pH-dependent cell wall (CW) loosening. However, the role of expansins in controlling CW biomechanical properties in specific tissues and organs remains elusive. We monitored hormonal responsiveness and spatial specificity of expression and localization of expansins predicted to be the direct targets of cytokinin signaling in Arabidopsis (Arabidopsis thaliana).

PCYT2-regulated lipid biosynthesis is critical to muscle health and ageing.

Muscle degeneration is the most prevalent cause for frailty and dependency in inherited diseases and ageing. Elucidation of pathophysiological mechanisms, as well as effective treatments for muscle diseases, represents an important goal in improving human health. Here, we show that the lipid synthesis enzyme phosphatidylethanolamine cytidyltransferase (PCYT2/ECT) is critical to muscle health.

Leaky and waveguide modes in biperiodic holograms.

This study details a theoretical analysis of leaky and waveguide modes in biperiodic all-dielectric holograms. By tuning diffraction orders and subsequently confining local density of optical states at two distinct resonance wavelengths, we present a new class of highly sensitive refractive index biosensing platforms that are capable of resolving 35.5 to 41.

Cytoskeletal disorganization underlies PABPN1-mediated myogenic disability.

Muscle wasting and atrophy are regulated by multiple molecular processes, including mRNA processing. Reduced levels of the polyadenylation binding protein nucleus 1 (PABPN1), a multifactorial regulator of mRNA processing, cause muscle atrophy. A proteomic study in muscles with reduced PABPN1 levels suggested dysregulation of sarcomeric and cytoskeletal proteins.

Direct measurement of protein-protein interactions by FLIM-FRET at UV laser-induced DNA damage sites in living cells.

Protein-protein interactions are essential to ensure timely and precise recruitment of chromatin remodellers and repair factors to DNA damage sites. Conventional analyses of protein-protein interactions at a population level may mask the complexity of interaction dynamics, highlighting the need for a method that enables quantification of DNA damage-dependent interactions at a single-cell level. To this end, we integrated a pulsed UV laser on a confocal fluorescence lifetime imaging (FLIM) microscope to induce localized DNA damage.

Recent progress and current opinions in Brillouin microscopy for life science applications.

Many important biological functions and processes are reflected in cell and tissue mechanical properties such as elasticity and viscosity. However, current techniques used for measuring these properties have major limitations, such as that they can often not measure inside intact cells and/or require physical contact-which cells can react to and change. Brillouin light scattering offers the ability to measure mechanical properties in a non-contact and label-free manner inside of objects with high spatial resolution using light, and hence has emerged as an attractive method during the past decade.

Optical imaging spectroscopy for plant research: more than a colorful picture.

Optical imaging is a routine and indispensable tool in plant research. Here we review different emerging spectrally resolved optical imaging approaches and the wealth of information they can be used to obtain pertaining to the underlying chemistry, structure and mechanics of plants.

Brillouin Light Scattering Microspectroscopy for Biomedical Research and Applications: introduction to feature issue.

There has been a marked revival of interest in brillouin light scattering spectroscopy/microscopy over the last decade in regards to applications related to all optically studying the mechanical problems associated with systems of biological and medical interest. This revival has been driven by advancements in spectrometer design, together with mounting evidence of the critical role that mechanical properties can play in biological processes as well as the onset of diverse diseases. This feature issue contains a series of papers spanning some of the latest developments in the field of Brillouin light scattering spectroscopy and microscopy as applied to systems of biomedical interest.

Hydration and nanomechanical changes in collagen fibrils bearing advanced glycation end-products.

Accumulation of advanced glycation end-products (AGEs) in biological tissues occurs as a consequence of normal ageing and pathology. Most biological tissues are composed of considerable amounts of collagen, with collagen fibrils being the most abundant form. Collagen fibrils are the smallest discernible structural elements of load-bearing tissues and as such, they are of high biomechanical importance.

Probing Mechanical Properties in Biology Using Brillouin Microscopy.

Brillouin microscopy can be used to map the mechanical properties of samples in a noncontact and label-free manner, with potential applications in cell biology. Here, we provide an overview of the underlying principles and technology as well as the current challenges and outlook.

Simultaneous dual-channel imaging to quantify interdependent protein recruitment to laser-induced DNA damage sites.

Fluorescence microscopy in combination with the induction of localized DNA damage using focused light beams has played a major role in the study of protein recruitment kinetics to DNA damage sites in recent years. Currently published methods are dedicated to the study of single fluorophore/single protein kinetics. However, these methods may be limited when studying the relative recruitment dynamics between two or more proteins due to cell-to-cell variability in gene expression and recruitment kinetics, and are not suitable for comparative analysis of fast-recruiting proteins.

β-Catenin-dependent mechanotransduction dates back to the common ancestor of Cnidaria and Bilateria.

Although the genetic regulation of cellular differentiation processes is well established, recent studies have revealed the role of mechanotransduction on a variety of biological processes, including regulation of gene expression. However, it remains unclear how universal and widespread mechanotransduction is in embryonic development of animals. Here, we investigate mechanosensitive gene expression during gastrulation of the starlet sea anemone , a cnidarian model organism.

Axicon-based Bessel beams for flat-field illumination in total internal reflection fluorescence microscopy.

Total internal reflection fluorescence microscopy (TIRF-M) provides low-invasive high-contrast surface imaging with optical sectioning of typically 100-200 nm. Thus, TIRF-M has become an established tool for imaging surfaces, including cell membranes. For TIRF-M, a homogenous evanescent field of excitation over the whole field of view is generally desired for quantitative microscopy; however, this is not necessarily straightforward to generate with Gaussian beams.

A novel non-canonical PIP-box mediates PARG interaction with PCNA.

Poly(ADP-ribose) glycohydrolase (PARG) regulates cellular poly(ADP-ribose) (PAR) levels by rapidly cleaving glycosidic bonds between ADP-ribose units. PARG interacts with proliferating cell nuclear antigen (PCNA) and is strongly recruited to DNA damage sites in a PAR- and PCNA-dependent fashion. Here we identified PARG acetylation site K409 that is essential for its interaction with PCNA, its localization within replication foci and its recruitment to DNA damage sites.

Mapping the subcellular mechanical properties of live cells in tissues with fluorescence emission-Brillouin imaging.

Extracellular matrices (ECMs) are central to the advent of multicellular life, and their mechanical properties are modulated by and impinge on intracellular signaling pathways that regulate vital cellular functions. High spatial-resolution mapping of mechanical properties in live cells is, however, extremely challenging. Thus, our understanding of how signaling pathways process physiological signals to generate appropriate mechanical responses is limited.

The Expression of Tubb2b Undergoes a Developmental Transition in Murine Cortical Neurons.

The development of the mammalian brain requires the generation, migration, and differentiation of neurons, cellular processes that are dependent on a dynamic microtubule cytoskeleton. Mutations in tubulin genes, which encode for the structural subunits of microtubules, cause detrimental neurological disorders known as the tubulinopathies. The disease spectra associated with different tubulin genes are overlapping but distinct, an observation believed to reflect functional specification of this multigene family.

Spectrally coded optical nanosectioning (SpecON) with biocompatible metal-dielectric-coated substrates.

Fluorescence nanosectioning within a submicron region above an interface is desirable for many disciplines in the life sciences. A drawback, however, to most current approaches is the a priori need to physically scan a sculptured point spread function in the axial dimension, which can be undesirable for optically sensitive or highly dynamic samples. Here we demonstrate a fluorescence imaging approach that can overcome the need for scanning by exploiting the position-dependent emission spectrum of fluorophores above a simple biocompatible nanostructure.

Photounbinding of calmodulin from a family of CaM binding peptides.

Background: Recent studies have shown that fluorescently labeled antibodies can be dissociated from their antigen by illumination with laser light. The mechanism responsible for the photounbinding effect, however, remains elusive. Here, we give important insights into the mechanism of photounbinding and show that the effect is not restricted to antibody/antigen binding.

Defining a superlens operating regime for imaging fluorescent molecules.

It has been shown that thin metal-based films can at certain frequencies act as planar near-field lenses for certain polarization components. A desirable property of such "lenses" is that they can also enhance and focus some large transverse spatial frequency components which contain sub-diffraction limit details. Over the last decade there has been much work in optimizing designs to reduce effects (such as material losses and surface roughness) that are detrimental to image reconstruction.