Introducing Students to NMR Methods Using Low-Field¹H NMR Spectroscopy to Determine the Structure and the Identity of Natural Amino Acids

Abstract

Nuclear magnetic resonance (NMR) spectroscopy is a widely used analytical technique for molecular structure determination, and is highly valued in the fields of chemistry, biochemistry, and medicinal chemistry. The importance of NMR methods in the European (PhEur) and United States Pharmacopeia (USP) is steadily growing. However, undergraduates often have problems becoming familiar with handling the complex data. We have developed a simple experiment in which undergraduates, who are learning 1H NMR spectroscopy for the first time, investigate natural amino acids, and determine their structure and identity using low-field 1H NMR measurements and simple COSY experiments. These students see and learn the connection between the chemical shift of the αC-proton and the isoelectric point of the amino acid. They engage with the spectroscopic topic by acquiring their own spectra, and processing and interpreting the data. Understanding important natural amino acids and their physicochemical character is highly relevant to all students studying life sciences.

Benchtop NMR Spectroscopy of Prebiotically-Relevant Peptide Reactions Enabled by Salt-Induced Chemical Shift Dispersion

“…The influence of protonation on the chemical shifts of amino acids is well-known, including measurements by benchtop NMR spectroscopy. 31 Specific ion effects and changes in dielectric constant are also known to influence chemical shifts in 1 H NMR spectra of peptides. 24,25,32 The changes in chemical shift observed in the low-field NMR spectra of Gly 2 were consistent with changes in the corresponding high-field spectra (see Figure S3).…”

“…Low-cost instrumentation helps democratize scientific research by empowering teams of citizen scientists to make meaningful contributions to modern fields of inquiry. The pedagogical value of laboratory experiments that use amino acids and a benchtop NMR spectrometer to study the relationship of chemical structure, reactivity, and spectrometric analysis has been noted, 31 and these experiments are an appropriate introduction to the foundations of the kinetics experiments described here. These projects could also stimulate training and research in lessdeveloped countries whose academic institutions lack the resources to acquire and maintain a high-field instrument.…”

Au–Ag core–shell composite nanoparticles as a selective and sensitive plasmonic chemical probe for l-cysteine detection in Lens culinaris (lentils)

“…On this basis, they are classied into carbohydrates (e.g., glucose, fructose, sucrose) and amino acids (e.g., cysteine, histidine), which generally consist of carbon, hydrogen, nitrogen, oxygen, sulphur and phosphorus atoms, that are present as an active binding site in the biomolecules and play an essential role in metabolic processes in the human body. [1][2][3] L-Cysteine (2 amino-3-mercaptopropanoic acid, HSCH 2 CH(NH 2 ) COOH) is supplemented majorly through protein-rich foods and comprises one of the proteinogenic amino acids. It is found in protein-rich foods in large amounts.…”

Low Field NMR Determination of pKa Values for Hydrophilic Drugs for Students in Medicinal Chemistry

“…Although this analytical technique has been one of the most important techniques for structure identification for decades, it has been difficult to teach this as practical course containing students' experimental NMR spectroscopy because of the price of the instruments and the handling. The development of bench-top NMR spectrometers has made this kind of teaching possible [1][2][3]. Interest for complex and high molecular weight protein structures has been an inspiration for the amazing developments in the high-resolution nuclear magnetic resonance.…”

“…We focused on developing the experiments that stress the importance of the NMR techniques in pharmaceutical analytics and drug design. We previously published two experiments that deepened the understanding of structure determination [2] and quantification [1] using NMR spectroscopy. Generally, NMR spectroscopy in a student lab is regarded as a technique for structural determination.…”