Biochemical techniques are the laboratory methods researchers use to isolate, identify, measure, and manipulate the molecules of life. They range from century-old workhorses like centrifugation to cutting-edge tools like CRISPR-based diagnostics, and collectively they underpin nearly every advance in medicine, agriculture, and biotechnology. Understanding what these techniques actually do, even at a general level, makes it far easier to follow news about drug development, genetic testing, disease outbreaks, or food science. What follows is a practical tour of the most widely used and rapidly evolving methods in the field.
Separating and Purifying Molecules
Before you can study a protein, a lipid, or a piece of DNA, you usually need to pull it away from the thousands of other molecules in a cell. That separation step is often the first thing that happens in a biochemistry lab, and there are several ways to accomplish it.
One of the most common is gel electrophoresis, where an electric field drives molecules through a gel matrix. In the protein version known as SDS-PAGE, a detergent called sodium dodecyl sulfate coats each protein so that it carries a uniform negative charge, meaning the protein’s size alone determines how fast it moves through the gel’s tiny pores. Smaller proteins slip through quickly; larger ones lag behind. The result is a ladder-like pattern where each band represents proteins of a particular mass.
1Current Protocols Essential Laboratory Techniques. SDS‐Polyacrylamide Gel Electrophoresis (SDS‐PAGE)Once you know which band you want, you still need to fish that protein out in a pure form. Affinity chromatography is one of the fastest routes. A popular version involves engineering the target protein with a small tag made of histidine amino acids. When the mixture is passed over a column containing nickel ions, the tagged protein sticks while everything else washes through. A change in buffer then releases the protein in a single, relatively clean step.
2PubMed. Purification of His-Tagged ProteinsFor separating whole organelles rather than individual molecules, researchers turn to density gradient centrifugation. Cells are broken open, and the resulting slurry is spun at high speed through layers of sucrose or another dense medium. Different compartments settle at different levels according to their density, allowing isolation of, say, endosomes or Golgi membranes for downstream analysis.
3PubMed. Isolation of endocitic organelles by density gradient centrifugation These organelle preparations can then be analyzed by proteomics methods to catalog every protein inside them.4PubMed. Isolation of Golgi membranes from tissues and cells by differential and density gradient centrifugation
Identifying Proteins With Mass Spectrometry
Once proteins are separated and purified, figuring out exactly what they are often falls to mass spectrometry. The idea is straightforward: ionize a molecule so it carries a charge, accelerate it, and measure how fast it flies. Its mass-to-charge ratio reveals its identity. In practice, two ionization strategies dominate proteomics. Electrospray ionization (ESI) sprays a liquid sample into a fine mist of charged droplets, while matrix-assisted laser desorption/ionization (MALDI) embeds the sample in a crystalline matrix and blasts it with a laser pulse.
These two approaches are not interchangeable. A large comparison of more than 72,000 peptides found that only about 39 percent were identified by both ESI and MALDI, highlighting a strong complementary relationship between the methods. The peptides each technique detected differed in properties like charge, water-repelling character, and chemical modifications.
5PubMed. MALDI versus ESI: The Impact of the Ion Source on Peptide Identification Because of this complementarity, some workflows split the same sample and analyze it by both methods to maximize coverage of a protein’s sequence.6PubMed. Exploiting the complementary nature of LC/MALDI/MS/MS and LC/ESI/MS/MS for increased proteome coverage Running the two in parallel can also increase confidence in results when researchers are trying to quantify how much of a protein is present under different conditions.7PubMed. Trypsin catalyzed 16O-to-18O exchange for comparative proteomics: tandem mass spectrometry comparison using MALDI-TOF, ESI-QTOF, and ESI-ion trap mass spectrometers
Detecting Specific Targets With Antibody-Based Assays
Mass spectrometry is powerful but not always practical for routine diagnostics or clinical testing. For detecting a single known target quickly and cheaply, antibody-based assays are the go-to approach. The workhorse here is the enzyme-linked immunosorbent assay, or ELISA. In a sandwich ELISA, a “capture” antibody is stuck to a plate, the sample flows over it, and if the target molecule is present it gets trapped. A second “detection” antibody then binds the other end of the target, and an enzyme attached to that antibody produces a color change you can measure. The sandwich format improves both sensitivity and specificity because the target has to be recognized by two independent antibodies.
The sensitivity gains can be dramatic. One early development of the sandwich ELISA for measuring IgE antibodies to bee venom allergens found it was 10 to 20 times more sensitive than conventional indirect ELISA or radioallergosorbent testing.
8Journal of Immunological Methods. Increased sensitivity and specificity of a sandwich ELISA for measurement of IgE antibodies More recently, sandwich ELISAs have been developed for public health surveillance, such as an assay capable of detecting H7 subtype influenza A viruses at concentrations as low as 10 nanograms per milliliter of recombinant protein, with enough breadth to catch antigenically drifted strains.9PubMed. Establishment of sandwich ELISA for detecting the H7 subtype influenza A virus
Amplifying and Sequencing DNA
The polymerase chain reaction (PCR) remains one of the most transformative biochemical techniques ever developed. It copies a specific stretch of DNA exponentially, turning a few molecules into billions in under an hour. Quantitative real-time PCR (qPCR) adds the ability to measure how much DNA accumulates at each cycle, which is how scientists quantify gene expression or viral load. Two common detection chemistries serve this purpose. SYBR Green is a dye that fluoresces when it binds double-stranded DNA, making it cheap and easy to set up. The TaqMan approach uses a specially labeled probe that is chewed up during amplification, releasing fluorescence only when the correct target is copied. TaqMan is more expensive but more specific, since the probe must match the target sequence precisely.
10PubMed Central. Comparison of SYBR Green and TaqMan methods in quantitative real-time polymerase chain reaction analysis of four adenosine receptor subtypesOn the sequencing side, nanopore technology has emerged as a way to read long stretches of DNA in real time. Instead of copying the DNA and inferring the sequence indirectly, a nanopore system threads a single strand of DNA through a tiny protein channel embedded in a membrane. As each base passes through, it causes a characteristic disruption in an electrical current, which a detector translates into sequence information. The portability and speed of nanopore devices have made them useful in field settings, from tracking Ebola outbreaks to monitoring environmental samples.
11PubMed Central. An Introduction to Nanopore Sequencing: Past, Present, and Future ConsiderationsSeeing Molecular Structures
Knowing what molecules are present is one thing. Understanding their three-dimensional shapes is what explains how they actually work. Three major techniques dominate structural biology, each with distinct strengths.
X-ray crystallography, the oldest of the three, requires coaxing a purified protein into an ordered crystal. An X-ray beam is then shot through the crystal, and the resulting diffraction pattern is used to compute an electron-density map. The longstanding challenge has been the “phase problem,” where critical information is lost during diffraction. For decades, researchers solved this using experimental tricks like incorporating heavy atoms or selenium into the protein. That landscape shifted dramatically when AI-based structure prediction tools like AlphaFold arrived. One research group that had struggled for two years to solve a crystal structure using traditional phasing methods succeeded almost immediately when they used AlphaFold-predicted models for molecular replacement.
12PubMed. The X-ray crystallography phase problem solved thanks to AlphaFold and RoseTTAFold models: a case-study report Today, molecular replacement using AlphaFold models frequently eliminates the need for experimental phase determination altogether.13PubMed Central. Facing the phase problem
Cryo-electron microscopy (cryo-EM) sidesteps the need for crystals entirely. Purified protein is flash-frozen in a thin layer of ice, and an electron beam captures images of individual molecules in random orientations. Software then combines thousands of these images into a three-dimensional reconstruction. A key advantage is that cryo-EM can handle molecules that resist crystallization. The main challenge is sample quality: if the target falls apart or exists in too many different shapes, the reconstruction becomes blurry. Researchers often screen buffer conditions to stabilize the complex before imaging.
14PubMed Central. A Primer to Single-Particle Cryo-Electron MicroscopyNuclear magnetic resonance (NMR) spectroscopy works differently again. It places a protein in a strong magnetic field and detects the signals emitted by atomic nuclei as they absorb and re-emit radiofrequency energy. NMR is uniquely good at capturing how proteins move and flex, revealing short-lived conformational states and transient interactions with binding partners that crystallography and cryo-EM would miss.
15PubMed Central. Emerging solution NMR methods to illuminate the structural and dynamic properties of proteinsWatching Molecules Interact in Real Time
Knowing a protein’s structure is only part of the story. Understanding which molecules it talks to, and how tightly, requires interaction-measurement tools. Two stand out for their versatility.
Förster resonance energy transfer (FRET) works by labeling two proteins of interest with different fluorescent tags. When the proteins come close together, energy transfers from the “donor” tag to the “acceptor” tag, changing the fluorescence signal. Because this energy transfer only happens efficiently over very short distances (around 10 nanometers or less), a FRET signal is strong evidence that the two proteins are physically interacting.
16PubMed Central. FRET-FLIM to Determine Protein Interactions and Membrane Topology of Enzyme Complexes When combined with microscopy, FRET can map these interactions inside living cells, providing spatial and temporal detail that test-tube experiments cannot.17PubMed. Imaging protein-protein interactions using fluorescence resonance energy transfer microscopy
Surface plasmon resonance (SPR), by contrast, measures interactions on a sensor chip outside the cell. One partner is attached to the chip surface, and the other is flowed over it in solution. When binding occurs, it changes the mass at the surface, which shifts the angle at which light is reflected. SPR provides real-time readouts of both how fast molecules bind, how fast they fall apart, and the overall binding strength. It requires no fluorescent labels, works with small amounts of material, and is widely used in drug discovery to screen how well candidate molecules stick to their targets.
18PubMed. Surface plasmon resonance spectroscopy for characterisation of membrane protein-ligand interactions and its potential for drug discovery19PubMed Central. Use of Surface Plasmon Resonance (SPR) to Determine Binding Affinities and Kinetic Parameters Between Components Important in Fusion Machinery
Measuring What Enzymes Do
Enzymes are the catalysts that drive virtually every reaction in a living cell, and measuring how fast they work is fundamental to biochemistry. Most enzyme activity assays track the appearance of a product or the disappearance of a starting material over time. Continuous assays, where the readout happens in real time, are preferred because any problems or artifacts can be spotted immediately rather than discovered after the fact.
20PubMed Central. Kinetic modelling: an integrated approach to analyze enzyme activity assaysA good example is a spectrophotometric assay for peptide deformylase, an enzyme involved in bacterial protein processing. Because the reaction produces a change in light absorption, researchers can follow it directly on a standard laboratory spectrophotometer, making the same setup useful for determining how the enzyme responds to different pH levels, how quickly it processes different substrates, and whether a candidate drug slows it down.
21PubMed. A direct spectrophotometric assay for peptide deformylaseTracking Metabolism With Isotope Tracing
Enzymes do not work in isolation. They are organized into metabolic pathways where the product of one reaction feeds into the next, forming a complex web of chemical conversions. Understanding how material flows through this web is the goal of metabolic flux analysis. One powerful approach involves feeding cells nutrients labeled with carbon-13, a stable, non-radioactive isotope. As the labeled atoms move through different metabolic reactions, mass spectrometry or NMR can track where they end up, revealing which pathways are most active.
22PubMed Central. 13C metabolic flux analysis: Classification and characterization from the perspective of mathematical modeling and application in physiological research of neural cellThe choice of which labeled nutrient to use matters enormously. A study evaluating multiple carbon-13-labeled forms of glucose and glutamine in tumor cells found that different tracers gave very different levels of precision for different parts of the metabolic network. For glycolysis and the pentose phosphate pathway, glucose labeled at positions one and two gave the best results, outperforming the more commonly used form labeled only at position one. For the citric acid cycle, uniformly labeled glutamine was the strongest choice.
23PubMed Central. Evaluation of 13C isotopic tracers for metabolic flux analysis in mammalian cells Beyond single-cell studies, untargeted metabolomics using liquid chromatography coupled to high-resolution mass spectrometry has expanded the scope to profiling hundreds of metabolites at once in complex samples like cereal grains, helping to identify biochemical differences linked to flavor, disease susceptibility, and crop breeding.24Journal of Chromatography Open. Untargeted metabolomics approaches for the characterization of cereals and their derived products by means of liquid chromatography coupled to high resolution mass spectrometry
CRISPR as a Biochemical Swiss Army Knife
CRISPR-Cas9 gene editing has become one of the defining biochemical techniques of the past decade. The system uses a short guide RNA to direct the Cas9 protein to a specific spot in the genome, where it cuts both strands of the DNA. The cell then repairs the break, and depending on the repair pathway, researchers can knock out a gene, correct a mutation, or insert new genetic material. Target recognition requires a short flanking sequence called a protospacer adjacent motif (PAM), and the cut happens a few bases upstream of it.
25PubMed Central. Mechanism and Applications of CRISPR/Cas-9-Mediated Genome Editing26PubMed. CRISPR-Cas9 Structures and Mechanisms
Beyond editing, CRISPR proteins have been repurposed as diagnostic sensors. Cas12, for instance, has a “collateral cleavage” activity: once it locks onto its target DNA, it starts indiscriminately cutting nearby single-stranded DNA. By designing a reporter molecule that fluoresces when cleaved, researchers can detect the presence of a specific DNA sequence with high sensitivity.
27PubMed Central. Solid-Phase Collateral Cleavage System Based on CRISPR/Cas12 and Its Application toward Facile One-Pot Multiplex Double-Stranded DNA Detection A related protein, Cas13, does the same thing with RNA targets, and its collateral RNA cleavage has been harnessed for rapid, portable nucleic acid detection, including COVID-19 diagnostics.28Communications Biology. Temporal dynamics of collateral RNA cleavage by LbuCas13a in human cells
Reading Gene Expression at the Single-Cell Level
Traditional methods for measuring gene expression, like qPCR or bulk RNA sequencing, average the signal across millions of cells. That averaging hides the fact that individual cells within the same tissue can behave very differently. Droplet-based single-cell RNA sequencing (scRNA-seq) addresses this by encapsulating individual cells in tiny oil droplets, each containing a unique molecular barcode. The RNA from each cell is tagged with that barcode, and after sequencing, researchers can trace every transcript back to the cell it came from. This approach has revealed previously invisible cell subtypes in tumors, developing embryos, and immune tissues.
29PubMed Central. Droplet-based single-cell RNA sequencing: decoding cellular heterogeneity for breakthroughs in cancer, reproduction, and beyondA limitation of scRNA-seq is that cells must be removed from their tissue, destroying information about where they were located. Spatial transcriptomics methods fill that gap by measuring gene expression directly in intact tissue slices, preserving the spatial context. Some approaches stamp barcoded probes onto a tissue section, while others use fluorescent labeling and repeated rounds of imaging. Combining spatial gene expression maps with AI-driven analysis of tissue morphology is a fast-moving area, allowing researchers to link what a cell looks like under a microscope with what genes it is expressing.
30PubMed Central. Spatial Transcriptomics: Emerging Technologies in Tissue Gene Expression Profiling31Nature Communications. Combining spatial transcriptomics with tissue morphology
Mapping Where Proteins Meet DNA
Genes are regulated by proteins called transcription factors that bind specific stretches of DNA to switch genes on or off. Identifying exactly where in the genome a particular transcription factor binds is the job of chromatin immunoprecipitation followed by sequencing (ChIP-seq). The procedure cross-links proteins to DNA inside living cells, breaks the DNA into small fragments, and uses an antibody to pull down fragments attached to the protein of interest. Sequencing those fragments and mapping them back to the genome reveals the binding sites.
32PubMed Central. Role of ChIP-seq in the discovery of transcription factor binding sites, differential gene regulation mechanism, epigenetic marks and beyondChIP-seq has scaled remarkably well. In prokaryotic organisms, the technology is already capable of mapping binding sites for every DNA-binding protein in the genome.
33PubMed. Transcription Factor Binding Site Mapping Using ChIP-Seq In eukaryotes, where genomes are larger and regulation more complex, ChIP-seq data have become a standard input for understanding how gene expression patterns differ between healthy and diseased tissues, and for identifying the epigenetic marks that control long-term gene silencing or activation. The method has also proven useful for discovering that transcription factors often work in complexes rather than alone, with computational analysis of ChIP-seq peaks revealing which factors tend to bind the same genomic regions.34Nucleic Acids Research. Inferring transcription factor complexes from ChIP-seq data
How These Techniques Fit Together
What makes modern biochemistry powerful is not any single technique but the way researchers chain them together. A typical project might start with cell fractionation to isolate a compartment, use mass spectrometry to catalog its proteins, apply cryo-EM to determine the structure of an interesting complex, run SPR to measure how tightly a drug candidate binds it, and finish with CRISPR to knock out the gene in a cell line and observe the consequences. Each technique answers a different question, and no one method gives the whole picture.
The trend across the field is toward higher resolution, lower input amounts, and greater throughput. Single-cell methods now capture information from thousands of individual cells in a single experiment. AI-based tools like AlphaFold are collapsing bottlenecks that used to stall structural projects for years. CRISPR diagnostics are moving nucleic acid detection out of centralized laboratories and into clinics and even homes. For anyone trying to understand a biological question, from how a cancer cell rewires its metabolism to why a crop variety resists drought, these biochemical techniques are the toolkit that turns curiosity into data.