Educational guides and overviews on research peptides, what they are and how they're studied in the laboratory. For research use only.
Stepwise assembly degrades with chain length, and a convergent route changes what the dominant impurity is. This covers protected fragment preparation on hyper-acid-labile resins, the epimerisation problem at the activated C-terminal residue, the reagents and solvents that suppress it, and why protected-fragment solubility can critically influence the outcome.
Read moreIon exchange ranks peptides by the charge they carry at the pH you chose, not by how much non-polar surface they can bury. How to pick the exchanger and the pH from side-chain pK values, when a salt gradient beats a pH gradient, why these columns are never purely charge-driven, and what a deamidation charge variant does and does not show.
Read moreReversed-phase and HILIC fail on different peptides. How the water-enriched layer retains polar sequences, how bare silica, amide and zwitterionic phases diverge, why equilibration and sample diluent govern reproducibility, and what the electrospray gain is worth once the analyte is a peptide rather than a small molecule.
Read moreTrace metals arrive in peptide work through palladium deprotections, copper ligations, nickel columns and steel surfaces, at levels no UV chromatogram resolves. What ICP-MS measures in a digested peptide matrix, and what the number does not license.
Read moreThree assays, three different chemistries, three different answers. What BCA counts in copper reduction, what Bradford counts in arginine, what the Folin step counts in Lowry, which buffers and detergents corrupt each, and why a BSA calibration slope is an assumption rather than a measurement when the analyte is a short synthetic sequence.
Read moreA donor and a quencher flanking the scissile bond report any cut between them; a coumarin leaving group reports one bond and carries no prime side. How the inner filter effect caps your substrate titration, why kcat/KM is often the only constant you can honestly report, and which controls decide whether the trace means anything.
Read moreAn ensemble FRET reading is one number that a two-state mixture and a homogeneous population produce alike. What a distribution of single-molecule efficiencies adds, where the Forster radius makes you blind, what site-specific double labelling costs in purification, how blinking and tethering can manufacture dynamics that are not there, and the controls that test whether they did, and why an uncorrected efficiency is only a proximity ratio.
Read moreDesigned self-assembly and undirected fibrillation are described by the same models; what separates them is a stated trigger, a stated concentration window and a stated target morphology. How alternating-charge, heptad-repeat, amphiphile and aromatic-stacking patterning set the architecture, why a critical aggregation concentration is not a gel point, and what rheology, microscopy and scattering each license you to conclude.
Read moreWhere crude extracts, reconstituted PURE and dialysis formats actually differ, why the energy system rather than the template usually decides when a batch reaction stops, how a linear PCR template survives an E. coli extract, and what a yield figure measured on a reporter protein does not tell you about a peptide.
Read moreA labelled twin spiked into the tube normalises everything downstream of the spike and nothing upstream of it. Where to introduce the standard, which nuclide to label with, how the standard's own assigned amount turns into systematic error, and what the ratio does not license you to say.
Read moreDeveloping an analytical reversed-phase peptide method: why the LSS slope S varies with peptide charge and length so gradient steepness reorders peaks, how to read scouting runs, what alkyl chain length, pore size and pressure actually change, and where the TFA-versus-formic-acid choice trades chromatographic resolution against MS response.
Read moreDLS records how fast a scattered-intensity flicker decorrelates; the radius arrives afterwards, from a sphere model you supplied. What cumulants and the polydispersity index license, why the sixth-power intensity weighting makes a trace of aggregate so visible, and why oligomeric state is a mass question answered by SEC-MALS rather than by a hydrodynamic radius.
Read moreOne-dimensional gradients for peptides saturate at a practical peak capacity of about several hundred, and adding a second dimension does not simply multiply that. How orthogonality is estimated and what the number licenses, how undersampling broadens first-dimension peaks and where the penalty actually falls, how dilution, trapping and active modulation handle solvent mismatch while salt needs a separate answer, and what the high-pH/low-pH, SCX and HILIC pairings each measured.
Read moreImpedance and dynamic mass redistribution read a whole-cell rearrangement, not a pathway. What each sensor physically integrates, what the kinetic trace holds that an endpoint read discards, how selective inhibitors put pathway identity back in, and why adhesion, confluence and cell background can set the amplitude before the ligand does.
Read moreConfiguration decides which membrane face a peptide can reach; the voltage protocol decides whether a gating shift is visible at all; series resistance error and adsorptive loss can decide whether the resulting numbers mean anything. What each measurement licenses, and what it does not.
Read moreSubtiligase is subtilisin re-engineered so that an alpha-amine, not water, resolves the acyl-enzyme. What the S221C/P225A pair actually bought, where the synthesis-to-hydrolysis ratio is set, why N-terminal selectivity turns the enzyme into a proteomics reagent, and how the junction constraint differs from native chemical ligation and from the transpeptidases.
Read moreA spot is never weighed, so the membrane gives you a rank and not a concentration. How cellulose hydroxyls are derivatised and loaded, cleavable versus non-cleavable linkers and what leaves with the peptide, why an 87-91% per-cycle coupling yield makes negatives the fragile result and per-spot purity unknowable, and the controls that separate real binding from detection-reagent cross-reactivity and the ring spot effect.
Read moreWhy a proton integral is a primary content measurement, how referencing and relaxation decide whether it is true, and what qNMR settles about a peptide that HPLC area percent and amino acid analysis cannot.
Read moreReporter, balancer and reactive group; why the same peptide labelled with different tag variants comigrates as one precursor, and why that precursor is rarely alone in the isolation window; what incomplete NHS labelling does to a ratio; how far co-fragmentation compresses fold changes, and what MS3 costs to fix it.
Read moreDIA fragments everything inside a fixed ladder of isolation windows instead of selecting precursors, trading acquisition-stage selectivity for near-complete data matrices. Window design, chimeric spectra, library choice and FDR estimation decide what the resulting numbers actually support.
Read moreDSC records the excess heat a peptide absorbs as it unfolds, so the enthalpy is an integral rather than a fit. What the thermogram gives you — Tm, calorimetric and van't Hoff enthalpy, heat capacity change — what the rescan and the scan-rate series have to establish before any of it is thermodynamics, and why a dye-reported apparent Tm is a different observable.
Read moreAmine coupling does not choose which residue attaches, and when the reactive residue sits close to the binding determinant, that can cost activity. This guide covers electrostatic preconcentration and the pH scout that finds it, thiol and capture chemistries, how ligand density shapes the constants you report, the flow-rate test for mass transport limitation, regeneration scouting, and reference-surface design.
Read moreA predicted structure is a hypothesis with a confidence array attached. What pLDDT and PAE each license you to conclude, why low confidence on a short peptide often reports disorder rather than failure, the alignment-depth problem for peptides and designed sequences, and what a model containing no ligand, ion, modification or membrane cannot settle.
Read morePumping reagent through a heated, packed bed replaces agitation with convection, and replaces coupling time with residence time and back pressure. What the in-line Fmoc-deprotection UV trace tells you each cycle, what it does not, and how the heat that buys minute-scale cycles reshapes aspartimide and epimerisation exposure.
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