2-(N-Morpholino)ethanesulfonic acid, often shortened as MES, grew out of a real need in the biochemical community. During the 1960s, researchers wanted reliable buffer solutions that wouldn’t interfere with biological processes or show unpredictability under varying lab conditions. Norman Good, the name behind so-called “Good’s buffers,” worked on this problem, giving us MES as a new tool in the expanding world of buffer chemistry. MES didn’t pop up from nowhere. The science behind buffering agents has always reflected the trial and error of practitioners who kept bumping into problems like buffer instability, contamination, or harsh interactions with the enzymes and cells under study. MES emerged as a sort of answer to this practical frustration, offering stability and compatibility.
MES looks unassuming—a white powder most days, a modest crystalline substance. Its importance hides quietly in thousands of scientific labs. It keeps samples, reactions, and tests within the desired pH range, protecting delicate biomolecules from swinging between acidic and basic environments. In molecular biology, MES usually steps in for cell culture work, protein purification, electrophoresis, and chromatography. Its low absorbance in the ultraviolet and visible range makes it popular for UV-transparent applications. Manufacturing grades span from research purity to high-purity pharmaceutical production, each batch labeled for its intended use, but most researchers recognize it as the backbone of many day-to-day molecular and cellular experiments.
MES comes as a white crystalline solid, showing high solubility in water. It has a molecular formula of C6H13NO4S, a molar mass just under 213.24 grams per mole, and a melting point close to 300 degrees Celsius, though it decomposes before boiling. The pKa hovers around 6.1 at room temperature, which lands MES squarely in the range needed for biological pH control. The morpholine ring provides some protection against oxidation, making it more dependable than classic buffers like Tris when working with sensitive samples. With a neutral odor and lacking any explosive or reactive tendencies under standard conditions, MES keeps everyone focused on the science rather than lab safety alarms.
Quality assurance in MES revolves around purity, moisture, pH control, and trace metals. Suppliers stick to tight specs—purity usually above 99%, slight tolerance for water content, and strict control over inorganic contaminants. Labels detail concentration, recommended storage, and shelf life, giving lab techs crucial information at a glance. Some suppliers provide batch-specific certificates of analysis, a move driven by researchers who cannot afford unseen impurities sabotaging months of work. The transition from “lab-grade” to “biotech-grade” reflects attention to trace endotoxins, nucleases, and particulates.
Synthesizing MES typically begins with morpholine reacting with ethylene chlorohydrin, forming the ethane chain connection, which then undergoes sulfonation. Industrial routes run several steps, emphasizing yield, safety, and waste management. The process aims for straightforward purification by crystallization, followed by drying. What matters for scientists using MES isn’t just efficiency. They care about process control—the confidence that every batch will buffer as expected, without haunting side products popping up weeks into an experiment. Laboratories reconstitute MES fresh for each use, dissolving the powder in water and carefully titrating to just the right pH.
MES proves hard to beat for inertness at physiological pH. Its structure resists attack from common laboratory oxidizers and reducers. Unlike Tris, which can sometimes join in side reactions, MES holds back, minimizing trouble for biochemists working with nucleic acids, proteins, or sensitive enzymes. Even so, MES isn’t invincible. It degrades under strong acidic or alkaline conditions, and intense heat leads to breakdown. Researchers looking for modified MES derivatives aim to tweak its buffering capacity or to tag it with fluorescent markers, though the parent compound stays the main choice in most buffer solutions.
MES goes by several aliases in catalogs: 2-(N-Morpholino)ethanesulfonic acid, 4-Morpholineethanesulfonic acid, and the simple shorthand of Good’s Buffer MES. Trade names depend on the supplier—Sigma-Aldrich and Thermo Fisher list it under standard buffer collections, while other manufacturers create branded lines for molecular biology or pharmaceutical markets. Researchers move quickly between names, but most stick to “MES buffer” when talking shop.
MES wins favor for its low toxicity and mild chemical footprint. Inhalation, ingestion, or skin contact pose little risk at common lab concentrations, though best practice demands splash protection, gloves, and safe handling around powdered chemicals. MES solutions don’t generate dangerous vapors, and spills clean up with water and routine disposal measures. Laboratories adopting ISO or GLP compliance rely on consistent buffer quality—and MES’s low risk profile fits neatly into workflows focused on safety audits and traceability. Chemists pay attention to dust inhalation when handling powders and always journal any accidental exposures out of respect for evolving occupational safety standards.
MES pops up in more corners of science than one might think. Cell and tissue culture groups reach for it to stretch the time between media changes. Protein chemists use MES in crystallization, purification, and modification reactions, where minimal interference matters most. DNA and RNA shops trust it for hybridization and electrophoresis, where old-school buffers just can’t keep the baseline straight. Plant physiology teams mix MES into hydroponic and soil experiments, where root systems suffer from sudden changes in acidity. Even industrial fermenters keep MES nearby to stabilize the pH of bacterial or yeast production runs, avoiding batch failures brought on by drifting buffer systems.
MES keeps evolving, not because the core chemistry needs change but because research keeps making new asks. Scientists keep pushing MES into higher-throughput applications, scale-up fermentation, and automated diagnostics. Mass production adapts around tighter purity controls, making sure researchers get the same results every time. MES has inspired exploration into related compounds—some buffered closer to neutral, some shifted toward extreme pHs required by specific enzyme studies or diagnostic kits. Drug discovery labs and environmental testing groups keep searching for tweaks to MES that deliver better performance in new assay formats. The evolution of MES comes from real lab stories—grad students stuck with strange results, postdocs hunting for lost protein signals, or clinical chemists comparing buffer performance in sample storage.
Long-term toxicity work on MES has revealed few worries. Acute oral and dermal studies in mammals point to low risk, and environmental tests show it breaks down without building up in soil or water. Regulatory bodies in Europe, North America, and East Asia haven’t flagged MES as a chemical of concern, which is rare relief compared to many organic lab reagents. Researchers still follow routine exposure controls—nobody wants chronic low-level dosing from careless spills or mishandling. End-users test each batch for endotoxins and bioburden, especially in sensitive in vitro or clinical setups, keeping the risks to an honest minimum. New studies occasionally look at interactions between MES and exotic cell lines or enzymatic pathways, all with the aim to confirm that the trusty buffer hasn’t picked up unexpected side effects as research needs change.
MES stands as a launching pad for new kinds of buffer chemistry. As researchers move toward single-cell sequencing, high-content screening, and synthetic biology, buffers like MES will find themselves tested in harsher, stranger environments than before. Industry pushes at lower detection limits and automation in diagnostic devices. Each leap requires buffers that won’t throw unpredictable wrenches into tight quality control systems. MES, after decades of steady service, still has room to grow—fine-tuned derivatives, better packaging, bulk formats, and even cleaner production pipelines. Scientists count on MES buffers not only for their current projects but in the hunt for answers that haven’t yet arrived at the lab bench.
The world of science runs on some chemicals many people never hear about. One of them, 2-(N-Morpholino)ethanesulfonic acid or MES buffer, holds a special place in life science research. Every time I worked in a molecular biology lab, containers of MES sat on shelves, ready for daily tasks. No hype, no buzz, just trusted reliability.
MES buffer plays a quiet but crucial role in experiments where pH control matters. Every cell, protein, and enzyme depends on the right pH. Even tiny shifts mess up results, waste precious samples, and kill time. MES keeps pH stable between 5.5 and 6.7, exactly where many biological systems function best. I used it almost every week during protein purification and cell culture projects. Without the stability MES brings, my data would turn useless because proteins behave unpredictably outside their comfort zone.
MES finds use all over biomedical research. Researchers use it during electrophoresis, live cell imaging, and enzymatic assays. Plant scientists depend on it to keep plant tissue culture media consistent, ensuring roots and shoots grow as expected. Some diagnostic kits in hospitals rely on MES to keep chemical reactions tuned just right, which helps labs detect disease markers more reliably. MES shows up in pharmaceutical research too, supporting work behind new drugs and treatments.
Not all buffers perform equally. MES doesn’t interact much with biological molecules, so it keeps experiments clean and clear. I learned early in my research that some buffers introduce background noise, making it impossible to measure what’s really going on. MES, with its low tendency to bind with ions like calcium or magnesium, gives scientists an honest baseline. Published studies back this up. For example, a review in the Journal of Biological Chemistry explained that MES remains one of the best picks for sensitive analyses because it stays chemically quiet.
Like any chemical, MES comes with handling precautions. Breathing in dust or getting it on skin can cause irritation. In our lab, gloves, safety glasses, and fume hoods kept us protected. Some colleagues wanted to swap MES for alternatives, worried about long-term safety or environmental impact. That started real conversations about greener lab practices. Solution? Scientists have begun testing plant-derived buffer solutions, though none match MES on all counts yet. The chemical supply industry continues searching for better options, and open communication about lab safety makes a difference. Improved training cut minor accidents in our group and helped people take chemical risks seriously.
The best safeguard against mistakes comes from combining experience with up-to-date facts. Regulatory bodies like OSHA and the American Chemical Society regularly publish new safety protocols. Reading these helped me catch little mistakes before they became big problems. Joining lab safety seminars and sharing lessons with teammates created a culture where people felt responsible for each other. MES, like many lab tools, supports discovery, but only when used with respect and understanding.
Stepping into a lab, one chemical shows up so often most people just call it MES. The full name, 2-(N-Morpholino)ethanesulfonic acid, gets tossed around in buffer recipes. This isn’t just another unpronounceable bottleneck on a shelf—it solves real problems biologists and chemists deal with daily. Its molecular weight, 195.2 grams per mole, hides plenty of practice and precision.
Every scientist has a story about weighing a compound for a buffer, glancing down at the digital scale, and hoping the calculations hold up. Getting the grams per mole wrong messes up experiments, whether you are titrating a protein or prepping a batch for cell culture. MES sits right in that comfort zone for weight—enough heft to handle easily, not too dense to cause solubility headaches.
I remember my first time prepping MES in grad school. The protocol kept it simple: they wrote 195.2 g/mol on the label, circled. If you use 1 liter water, you know how much acid to add to hit 1 molar. Get it wrong and pH curves sag or spike. Enzyme activities crash, and protein crystals shiver apart. The molecular weight keeps things reliable.
This acid stands out in biochemistry as one of those rare chemicals that does its job without fuss. With a pKa near physiological pH, MES buffers without fighting with sensitive cell systems. That allows proteins or nucleic acids to keep their shape and stay functional while experiments crank on. It isn’t reactive with magnesium or calcium either, which turns out to be a quiet blessing in genetics labs—many buffers might mess with these cations and kill the experiment.
MES does its work in plant labs, too. Growing roots and shoots in culture calls for a steady pH to avoid stunted growth. The buffer’s consistent molecular weight means even new students can follow the protocol, weigh out the right amount, and set things up without crashing the experiment.
There’s a lesson in this precision. Most seasoned lab workers don’t trust memory—they go back to the number every time. Suppliers like Sigma-Aldrich or Thermo Fisher provide the 195.2 g/mol value on every bottle, and labs update protocols as standards improve. Batch purity can shift slightly, but pure MES always tracks closely to that figure. This is especially crucial in big or repeated experiments where small errors scale up fast, eating up budgets and time.
Careful measurement anchors reliable science. Researchers depend on chemicals like MES to do what’s expected, each time and for everyone in the lab. With more transparency from chemical suppliers and better batch documentation, labs can trace back any odd result to a specific molecular weight or purity level that’s different from what’s posted. Checking—and double-checking—the value for MES is a step anyone in the scientific field should keep front-of-mind. Small habits keep discoveries on track, and that 195.2 grams per mole is a cornerstone.
Anyone working in a biochemistry or molecular biology lab recognizes 2-(N-Morpholino)ethanesulfonic acid. Known as MES buffer, this compound shows up in all sorts of buffer recipes. I’ve opened more than a few bottles over the years, and after seeing a fair share of caked solids, I’ve learned–organizing how you store MES makes life a lot easier and cleaner.
A simple walk through any research building tells a story of hot, humid summers and dry, frigid winters. MES powder left out for even a few days can clump badly or suck up moisture, making it crumbly or chunky. I’ve watched powders turn into difficult-to-weigh chunks just because someone left the bottle near the window. Storing MES in a cool, dry place matters. Many labs dedicate the bottom drawers of a cabinet for sensitive reagents like MES to keep sunlight and temperature swings at bay. Actual temperature ranges sit best between 2°C and 8°C if you want to really stretch shelf life.
Avoiding the refrigerator door shelf isn’t just a habit; it actually does more. The door area often experiences regular temperature changes as people grab things and close it again. A stable spot toward the back of the fridge keeps things steady. For those labs without much fridge space, keeping MES powder away from water sources (like sinks) and far from heating vents works fine.
Powdered buffers like MES don’t shrug off a little humidity the way salts might. Desiccant packets stashed in the bottle help. It might seem like an overcautious habit, but I’ve noticed fewer complaints about ruined batches once we started using silica gel packets and reminding everyone to screw the lid on tight. Fact: a study from Analytical Biochemistry points out how even brief exposure to moisture skews weight and concentration calculations, pushing experiments off track. If you’re weighing MES onto the scale, scoop out only what you need and put the bottle away fast to avoid ambient air damage.
It’s always tempting to just scribble “MES” onto a generic container, but clear labeling helps future-proof the lab. Expiry dates written on each container cut down on risky mistakes–I’ve seen undergrads grab a crusty bottle left from a previous semester, only to end up with wonky pH results. It helps if each stock bottle lists who first opened it too. This way, everyone knows who might have contaminated the contents or left the lid partly open.
Dissolved MES solutions face even bigger risks. Bacterial and fungal contamination can sneak in if bottles aren’t sterile. Filtering solutions, using sterile containers, and keeping everything under refrigeration can minimize the chances of spoiled stocks. I’ve seen cloudy buffer turn up in the fridge when someone left the cap loose. That means tossing the whole batch and losing a few hours of work. Autoclaving sometimes helps but check compatibility first, because MES can degrade above certain temperatures.
It always comes down to small habits: dry scoops, fast resealing, clean containers, and a bit of discipline. It’s not glamorous, but a culture of careful storage goes a long way. New team members can learn the ropes from the get-go. Labs that create quick signage and run short training chats save money and escape repeat frustrations. With reliable MES on hand, experiments run smoother and results stay consistent.
Anyone who’s spent time at a lab bench knows how unpredictable pH can knock even careful experiments off track. Nothing sours an afternoon like unstable readings or confused results. Researchers trust buffers like 2-(N-Morpholino)ethanesulfonic acid—usually called MES—to keep pH steady. This small, white powder gets used so often, folks can overlook what gives it its magic: the pKa value. For MES, that number is about 6.1 at 25°C.
MES stands apart from a flurry of buffer choices, often showing up across biochemistry, molecular biology, and plant research. Its pKa puts it squarely in the sweet spot for many life science experiments, especially those sticking near neutrality. Most enzymes, proteins, or cell cultures thrive between pH 5.5 to 7.0. With a pKa at 6.1, MES helps hold the line in these ranges.
pKa tells you where a buffer guards against big swings in pH. At or near its pKa, a buffer resists change from acids or bases getting tossed in. MES keeps pH stable around 6.1, which means it’s useful for many cellular and protein experiments where those molecules function best. If you step too far above or below that value, MES loses its edge and pH can jump a lot with just a nudge. Experience in college chemistry labs drove home how little margin you get outside these comfort zones: try pushing MES to pH 7.5, results start skating all over the place.
Ignoring the pKa means risking time, money, and credibility. This isn’t just theory. I’ve seen undergrads scramble to explain why their protein’s activity flatlined. Often, the real culprit traced back to buffers picked for convenience, not for the chemistry at hand. Messing up pH can twist enzymes out of shape or ruin yield. Sometimes a whole batch of valuable samples ends up in the trash. Biotech companies don’t accept results when basic prep gets fumbled.
The literature backs up why scientists rely on MES. According to Good et al., who first developed these biological buffers, MES’s pKa and low metal binding make it better for sensitive enzyme assays than many traditional buffers, like phosphate or Tris. MES hardly chelates divalent metals, so it doesn’t mess with cofactors. It’s also less prone to photodegradation. Most commercial MES stocks meet pharmaceutical purity standards, minimizing contamination risks. No buffer does every job, but MES had staying power thanks to decades of trust built on solid chemical footing.
Picking the right buffer still trips up plenty of new researchers. Simple solutions can help. Start with a clear rundown: double-check literature, use resources from the American Chemical Society or trusted university guides, and test buffer performance with controls. Document every buffer’s batch number and preparation details. Lab managers can organize a buffer shelf with guidance cards taped to each container, noting optimal ranges. Investing a little time up front means far fewer headaches later, and it keeps science honest and repeatable.
Anyone who has worked in a chemistry lab has come across a shelf lined with buffers. 2-(N-Morpholino)ethanesulfonic acid, usually called MES, shows up on those shelves a lot. MES makes life in the lab a bit easier by keeping pH levels steady, especially when you’re working with biological samples. I remember preparing buffers for a plant physiology experiment, measuring MES powder on an old digital balance that seemed to add an extra milligram if you so much as breathed in the room. No hazard suit, just a lab coat, gloves, and glasses—standard safety gear for a buffer like this.
People often ask if MES should worry them. Compared to more notorious chemicals, MES sits near the bottom of the danger list. High-quality sources like the PubChem database and Sigma-Aldrich’s safety data show that MES carries a hazard level similar to sodium chloride. It won’t explode, catch fire, or eat through your bench.
Swallowing MES by accident—never a good idea—produces mild symptoms if any. Skin might get irritated if you rub a lot on, but it doesn't go beyond some redness for most healthy adults. The dust can bug your eyes or nose. Still, I never saw a colleague collapse from it or scramble for the emergency shower. With over a decade running undergraduate labs, I watched hundreds of students pour MES solutions, mixing them using gloved hands. Minor spills, though rare, always cleaned right up with a paper towel and water.
The absence of acute toxicity does not mean MES belongs in the break room or should end up in the sink. Routine exposure to anything—no matter how mild—builds up risk over time. I’ve known researchers who cut corners on safety, then complained of rashes or nosebleeds weeks later and wondered why. Being careful with powders and washing after handling cuts down on problems.
MES doesn’t break down quickly once it leaves the lab. Scientists report that it drifts through water systems and may persist, potentially affecting aquatic organisms. No big disasters link MES to wildlife harm, at least not yet. Still, I don’t encourage dumping leftovers down the drain. Waste collection protocols exist for a reason. Proper chemical disposal costs time and money, but that effort closes the loop. Years supervising student research taught me that keeping waste out of public hands or sewers helps everyone.
No one should write off chemical safety as “common sense” just because a compound lacks a skull and crossbones. I teach newer lab workers to treat every bottle with respect, even MES. Read the label, print the Safety Data Sheet, store containers away from food, and never eat or drink in the lab. All that advice may sound basic, but it stops accidents before they start.
MES doesn’t pose any special threat so long as you treat it for what it is—a synthetic powder that keeps experiments running smoothly, not a toy. Safer handling, responsible disposal, and proper information always outshine complacency.
| Names | |
| Preferred IUPAC name | 4-morpholineethanesulfonic acid |
| Other names |
MES 2-(Morpholino)ethanesulfonic acid 4-Morpholineethanesulfonic acid |
| Pronunciation | /tuː ɛn mɔːˈfɒlɪnoʊ ˌɛθeɪnˈsʌlfɒnɪk ˈæsɪd/ |
| Identifiers | |
| CAS Number | 4432-31-9 |
| Beilstein Reference | 1714100 |
| ChEBI | CHEBI:39048 |
| ChEMBL | CHEMBL267467 |
| ChemSpider | 5609 |
| DrugBank | DB03754 |
| ECHA InfoCard | 100.052.430 |
| EC Number | 103-76-4 |
| Gmelin Reference | 87771 |
| KEGG | C02315 |
| MeSH | D008749 |
| PubChem CID | 5789 |
| RTECS number | NT4830000 |
| UNII | J41CSQ7QDS |
| UN number | Not regulated |
| CompTox Dashboard (EPA) | DTXSID3020256 |
| Properties | |
| Chemical formula | C6H13NO4S |
| Molar mass | 195.22 g/mol |
| Appearance | White crystalline powder |
| Odor | Odorless |
| Density | 1.054 g/cm³ |
| Solubility in water | miscible |
| log P | -2.2 |
| Acidity (pKa) | 6.1 |
| Basicity (pKb) | 5.8 |
| Refractive index (nD) | 1.484 |
| Dipole moment | 5.8167 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 317.8 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -552.8 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -2815 kJ/mol |
| Hazards | |
| Main hazards | Causes serious eye irritation. Causes skin irritation. May cause respiratory irritation. |
| GHS labelling | GHS07 Warning H319 P264 P305+P351+P338 |
| Pictograms | GHS07 |
| Signal word | Warning |
| Hazard statements | H319: Causes serious eye irritation. |
| Precautionary statements | P264, P270, P305+P351+P338, P337+P313 |
| NFPA 704 (fire diamond) | **1-1-0** |
| Lethal dose or concentration | LD₅₀ (oral, rat) > 10,000 mg/kg |
| LD50 (median dose) | LD50 (median dose): Oral, rat: >10,000 mg/kg |
| NIOSH | KWK70 |
| PEL (Permissible) | Not established |
| REL (Recommended) | 50 mg/m³ |
| Related compounds | |
| Related compounds |
MES sodium salt 2-(N-Morpholino)Propane-sulfonic acid (MOPS) HEPES PIPES TES |
