Learning about peptides
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Cleavage cocktails in Fmoc-SPPS: why scavengers determine whether a research peptide comes off pure
Every Fmoc-SPPS synthesis ends with a step that has at least as much influence on the eventual purity as the coupling chemistry itself: the cleavage. At this point the complete peptide, still...
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Capping and deletion sequences in Fmoc-SPPS: how a missed coupling undermines peptide purity
In the synthesis of research peptides via Fmoc-SPPS, not every coupling step runs to a hundred per cent. A small percentage of amino groups remains unreached, and without intervention those missed couplings...
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Resin choice in Fmoc-SPPS: Wang versus Rink Amide resin and the role of loading
In building a research peptide via solid-phase peptide synthesis (SPPS), attention often falls on the coupling chemistry: which activating reagent, which protecting groups, which solvent. A choice at least as decisive for...
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Protecting groups in Fmoc-SPPS: how orthogonality determines a successful peptide synthesis
In building a peptide chain via solid-phase synthesis (SPPS), every reactive side chain has to be shielded temporarily, or unwanted side reactions arise between amino acids that are not meant to be...
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Accelerated Stability Studies: How The Shelf Life Of Research Peptides Is Determined
An expiry date on a certificate of analysis often looks like a fixed fact, but behind that date usually sits a calculation model. Few laboratories have the luxury of following a peptide...
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Coupling Reagents In Peptide Synthesis: How HBTU And HATU Form Amide Bonds
In the synthesis of research peptides, forming an amide bond looks simple on paper: a carboxylic acid group of one amino acid reacts with the amino group of the next. In practice,...
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Fluorescent and biotin labelling of research peptides: techniques and considerations
Why researchers label peptides In many research set-ups it is not enough to know that a peptide engages in a particular interaction — one also wants to follow, quantify or visualise that...
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Inert atmosphere in storing research peptides: how nitrogen and argon counter oxidation
Cysteine-containing research peptides are among the most oxidation-sensitive molecules in a peptide library. The thiol group of cysteine reacts at even traces of dissolved oxygen, and the result is measurable: shifted HPLC...
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Analysing aggregation of research peptides: what size-exclusion chromatography reveals
Aggregation is one of the least visible but most disruptive phenomena in peptide research. A sample can look perfectly pure by mass spectrometry and HPLC and still behave unexpectedly in an assay...
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Isoelectric point of research peptides: how net charge governs solubility and aggregation
Anyone who works regularly with lyophilised research peptides knows the problem: a peptide that according to the certificate should be perfectly soluble still turns cloudy in a particular buffer, or precipitates after...
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N- and C-terminal modifications of research peptides: acetylation and amidation
Research peptides are almost always ordered with a specific sequence, but anyone looking closely at the specification often also sees a note about the termini: free N-terminal amine, free C-terminal acid, or...
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Circular dichroism: mapping the secondary structure of research peptides
Most of the analytical techniques covered in earlier articles on this blog — HPLC, mass spectrometry, UV-Vis spectrophotometry, amino acid analysis — address the question of how much peptide is in a...
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