6 – Microscopy

Fluorophore selection is important. I have often been asked by my facility users which fluorophore is best suited for their experiments. The answer to this is mostly dependent on whether they are using a widefield microscope with set excitation/emission cubes or a laser based system that lets you select the laser and the emission window. Once you have narrowed down which fluorophores you can excite and collect the correct emission, you can further refine the specific fluorophore that is best for your experiment.  In this blog  we will discuss how to determine what can work with your microscope, and how…

Image quality is critical for accurate and reproducible data. Many people get stuck on the magnification of the objective or on using a confocal instead of a widefield microscope. There are several other factors that affect the image quality such as the numerical aperture of the objective, the signal-to-noise ratio of the system, or the brightness of the sample.  Numerical aperture is the ability of an objective to collect light from a sample, but it contributes to two key formulas that will affect your image quality. The first is the theoretical resolution of the objective. It is expressed with the…

TIRF is not as common as other microscopy based techniques due to certain restrictions. We will discuss these restrictions, then analyze why it might be perfect for your experiment.  TIRF relies on an evanescent wave, created through a critical angle of coherent light (i.e. laser) that reaches a refractive index mismatch.  What does it mean in practice?  A high angle laser reflects off the interface of the coverslip and the sample. Although the depth that this wave penetrates is dependent on the wavelength of the light, in practice it is approximately 50-300nm from the coverslip. Therefore, the cell membrane is…

2020 was a difficult year for many, with their own research being interrupted- either by lab shutdowns or recruitment into the race against COVID-19. Despite the challenges, scientists have continued to be creative and have pushed the boundaries of what is possible. These are the techniques and technologies that every microscopist was envious of in 2020. Spatially Resolved Transcriptomics Nature Methods declared that spatially resolved transcriptomics was the 2020 method of the year. These are a  group of methods that combine gene expression with their physical location. Single-cell RNA sequencing (scRNAseq) was originally developed for cells that had been dissociated…

As biologists, we study the process of life, however, it’s intricacies cannot be captured by a snapshot in time. Generally, the easiest imaging experiments are those where the samples are stained, fixed, and imaged within a few days of procurement, but that too doesn’t capture the dynamic processes common in cells and organisms. Live cell imaging when combined with reporters serves as a powerful tool to provide solid imaging data. Cameleon —one of the first reporters— was developed in 1997 in Roger Tsien’s lab.  Cameleon is a green fluorescent protein (GFP) that undergoes a conformational change in the presence of…

As scientists, we need to perform image analysis after we’ve acquired images in the microscope, otherwise, we have just a pretty picture and not data. The vocabulary for image processing and analysis can be a little intimidating to those new to the field. Therefore, in this blog, I’m going to break down 7 terms that are key when post-processing of images. 1. RGB Image Images acquired during microscopy can be grouped into two main categories. Either monochrome (that can be multichannel) or “RGB.” RGB stands for red, green, blue – the primary colors of light. The cameras in our phones…

In an ideal world, we would be able to use fluorophores that don’t have any overlap in emission spectra and autofluorescence wouldn’t obscure your signal. Unfortunately, we don’t live in such a world and often have to use two closely related dyes – or contend with fluorescent molecules that are innately part of our sample. Fluorescent molecules include chlorophyll, collagen, NADPH, and vitamin A.  One example that I recently encountered was developing a new probe for lipids. The reviewers requested a direct comparison of the new dye to Nile Red in the same sample. Both dyes would localize to the…

A lot of microscopy assays are focused on labeling and imaging proteins. We often use antibodies against specific protein antigens or fuse a fluorescent protein to a protein of interest.  These methods cover many applications, but maybe you are interested in viral RNA, gene duplication, or need a counterstain to label the nucleus. You can’t fuse a protein to nucleic acids, so where should you start? Try these 5 assays to image nucleic acids: Nucleic Acid Dyes  Nucleic acid dyes are small molecules that increase fluorescence when bound to nucleic acids.  They can bind DNA, RNA, or both, but do…

Designing microscopy experiments related to infectious diseases and antivirals can be challenging, but there's never been a more vital time than right now to design adequate microscopy experiments. The novel coronavirus (SARS-CoV-2) emerged in Wuhan, China, in December 2019 and spread across the globe becoming the pandemic that the world is reeling with today. Currently, COVID-19  has no targeted therapies approved by the FDA, so the best coronavirus prevention happens through social distancing and good hygiene practices. However, companies are rapidly testing candidate molecules and vaccines as fast as they can. Initial tests suggest there may be some drugs that…

Imaging deep into tissues has always been difficult, whether challenges derive from working distance, light absorption by natural chromophores, or light scattering by mismatched refractive indexes. Cells are full of mismatched refractive indexes, which is great for DIC but bad for fluorescence. These fluids have a refractive index of 1.35 while lipids and membranes like the golgi and mitochondria have a refractive index of 1.45. Structural proteins such as actin or microtubules can have a refractive index greater than 1.5 – this all means that light will not follow a straight line as it enters and exits the samples. Thus,…

Have you ever noticed how painful it can be to purchase a new microscope? It would be hard to miss – this can be a frustrating process. A lot of scientists and students consider the new microscope hunt quite scary for a variety of reasons. It might be that you’re worried you won’t get the right microscope and that you’ll regret it, or you may find that dealing with salespeople, in general, makes you kind of uncomfortable. But remember, salespeople are just human beings like you and me, and if we can treat them as such, the whole process of…

There are 7 different common “artifacts” that may be affecting the quality of your imaging. Before digging into the details, let’s begin by defining an artifact: Essentially, it is any error introduced through sample preparation, the equipment or post-processing methods. This is an important concept to grasp because the effects can cause false positives or negatives, and they can physically distort your data. This is, of course, at odds with your mission to obtain reliable quantitative data. So what can you do to stop these artifacts? The problems can range from dirty objectives to bigger issues like light path aberrations.