Attached Proton Test, an 'APT' experiment for structural elucidation

Attached Proton Test, an 'APT' experiment for structural elucidation

A key step towards elucidating structures with NMR spectroscopy is the assignment of signals to specific groups within the molecule being analyzed. Two experiments, DEPT (Distortionless Enhancement by Polarization Transfer) and APT (Attached Proton Test), are typically used to aid this process with 13C NMR spectra.1 Both experiments are similar in that the number of attached protons (i.e. the multiplicity) is revealed by the phase of the 13C NMR signals. The key difference between the DEPT and APT experiment is that signals for quaternary carbons are observed in the APT experiment.

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Unlocking the Key to Enzymes: Studying Enzyme Kinetics

Unlocking the Key to Enzymes: Studying Enzyme Kinetics

By virtue of its quantitative nature, NMR spectroscopy is increasingly becoming the method of choice to monitor a reaction and determine its kinetic parameters. We’ve demonstrated the ability of the NMReady-60 to monitor a reaction and subsequently extract kinetic parameters in a previous blog post. In this blog post, I’d like to show how the NMReady-60 can be used to study enzyme kinetics. Adapted from a Journal of Chemical Education article published by Olsen and Giles, the enzymatic hydrolysis of N-acetyl-DL-methionine by porcine acylase was studied.

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How strong was your coffee this morning?

How strong was your coffee this morning?

Who doesn’t want to start the day with a warm cup of coffee? Coffee has a stimulating effect on humans because of its caffeine content and for that reason it has become one of the most popular drinks in the world. Some clinical studies actually suggest that small amounts of caffeine everyday might be beneficial for adults. In this blog I am going to highlight an experiment done in collaboration with the Swager group at MIT using an organometallic complex to quantify the caffeine content in regular coffee without sample preparation!

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To D2O or not to D2O?

To D2O or not to D2O?

In the average case one can simply dissolve an analyte in an appropriate deuterated solvent and acquire a simple 1D spectrum to obtain all the required structural information.  However, sometimes doing so may not provide you with all of the information you need!  It is not uncommon to encounter labile proton peaks in functional groups such as alcohols, amines, amides, and carboxylic acids. 

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A watched pot never boils… how to monitor reactions the easy way!

A watched pot never boils… how to monitor reactions the easy way!

When monitoring reaction progress for determination of reaction kinetic parameters, NMR spectroscopy has increasingly become the method of choice. The ease in which one can calculate the concentration changes of a substrate being consumed or a product being formed over time, directly from peak integration are the reason behind this.

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The Dangers of Making Too Many Assumptions. Electronegativity, Acidity, and Chemical Shift

The Dangers of Making Too Many Assumptions. Electronegativity, Acidity, and Chemical Shift

Last month (which you can see here), we learned about how an acidic proton behaves in a 1H NMR experiment, particularly when it’s surrounded by D2O. For example, when an H+ leaves CH3COOH to join an accommodating D2O molecule, the resulting acetate (H3CCOO–) segment is reasonably comfortable bearing that negative charge. This phenomenon is the reason the solution is “acidic” in the first place. But why is acetate so capable of dealing with this negative electronic charge?

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#Worldbookday

I don’t know if you check out Compound Interest (@compoundchem) or not, but if you don’t you should probably consider remedying that IMMEDIATELY!  Pretty much every single time that I read it I have a “HMMMM, OHHHH, Cool! I had no idea!” moment.  Today, was no exception. They have interesting real world chemistry examples of …

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