In the world of peptide synthesis, a game-changing innovation has emerged – a remarkable cocktail designed to enhance the cleavage and deprotection of methionine-containing peptides. This groundbreaking concoction, known as Reagent H, is set to transform the landscape of solid-phase peptide synthesis, particularly for those using the 9-fluorenylmethoxycarbonyl (Fmoc) methodology.

Unveiling Reagent H: Your Key to Methionine Side-Chain Protection

Reagent H, comprised of trifluoroacetic acid (81%), phenol (5%), thioanisole (5%), 1,2-ethanedithiol (2.5%), water (3%), dimethylsulphide (2%), and ammonium iodide (1.5% w/w), has been meticulously crafted to minimize the pesky oxidation of methionine side chains during synthesis. Its exceptional performance is exemplified in the synthesis of a model pentadecapeptide from the active site of DsbC, a pivotal player in protein disulfide bond formation.

The Triumph of Reagent H: Methionine Sulphoxide Conquered

When put to the test, Reagent H outshone its competitors, cocktails K, R, and B. The crude peptides obtained from these widely used mixtures contained a staggering 15% to 55% of methionine sulphoxide. However, Reagent H demonstrated its prowess by yielding pristine peptides devoid of methionine sulphoxide. Remarkably, even when 1.5% w/w NH4I was added to cocktails K, R, and B, they couldn’t match the perfection achieved by Reagent H, although their yield of the desired peptide fell short.

Unraveling the Mysteries: A Closer Look at Reagent H’s Mechanism

But how does Reagent H achieve this remarkable feat? We delve into the proposed mechanism behind its in situ oxidation of cysteine, shedding light on its impressive ability to safeguard methionine side chains while delivering high-quality peptides.

In the world of peptide synthesis, Reagent H stands as a beacon of hope for researchers seeking purity, precision, and protection in their work. Its ability to minimize methionine side-chain oxidation is nothing short of revolutionary, promising a brighter and more efficient future for peptide synthesis enthusiasts. Say goodbye to impurities and hello to perfection with Reagent H.

Many sensory declines come along with aging, one of much concern being sight. That being said, there is a need for much more research on the visual changes associated with such aging. Specifically, the changes of rod bipolar cells and their ribbon synapses due to aging are an area of interest, along with the complex calcium systems at work. Using a zebrafish model, peptides help determine the effects of aging on vision and the retina.

TAMRA-RBP peptides tag rod bipolar cells

Zebrafish were used for this experiment thanks to their unique roles as model organisms; they share 70% genomic similarity with humans, and their short lifespan offers the chance to study life cycles in a few short years while still comparable to human aging over decades. Researchers compared data between middle-aged (MA, 18-months-old) and older-aged (OA, 36-months-old) zebrafish, equating to human ages of approximately 38 and 75 years of age, respectively. Using TAMRA ribbon-binding peptides from LifeTein, the team was able to observe changes between the two ages of zebrafish.

What was discovered was a decreased number of synaptic ribbons and increased ribbon length in the OA models. Further, there were many alterations to the local calcium dynamics of the system, implying a more complex change to vision deterioration than initially expected. The model shows how subtle changes could have vast implications for disease models where these alterations may be amplified, and surely sheds more light on how human vision may decline with age.

Abhishek P Shrestha, Nirujan Rameshkumar, Johane Martins Boff, Rhea Rajmanna, Thadshayini Chandrasegaran, Frederick E Courtney, David Zenisek, Thirumalini Vaithianathan
bioRxiv 2023.09.01.555825; doi: https://doi.org/10.1101/2023.09.01.555825