In the world of biotherapeutics, bigger often means better — at least when it comes to circulation time in the bloodstream. One of the most widely used strategies to extend the half-life of protein drugs is PEGylation: attaching polyethylene glycol (PEG) chains to a therapeutic protein. The added polymer shields the protein, reduces immune clearance, and improves pharmacokinetics.<h4>PEGylation creates a major analytical challenge</h4>PEG is large and polydisperse (a distribution of chain lengths), and when attached to already complex, glycosylated proteins, it creates a molecular puzzle. How many PEGs are attached? Where are they attached? Are there impurities left behind?In this study, <a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.jproteome.5c00788?goto=supporting-info">Charge Detection Mass Spectrometry and a Glu-C/Lys-C Digestion-Based Data-Dependent Approach Suggest Mono-PEGylation of a Heterogenous Therapeutic Protein</a>, researchers developed a powerful mass spectrometry workflow that answers these questions — using Orbitrap-based charge detection mass spectrometry and a clever bottom-up strategy. The result? A confident determination that the therapeutic protein carries a single ~30 kDa PEG, along with precise mapping of its attachment sites.Let’s break down how they did it.<h3>The analytical problem: pegylation meets glycosylation</h3>The therapeutic protein studied here is already highly heterogeneous:<ul><li>165 amino acids</li><li>3 N-glycosylation sites</li><li>1 O-glycosylation site</li></ul>Add a ~30 kDa polydisperse PEG on top of that, and conventional mass spectrometry quickly runs into trouble:<ul><li>PEG ionizes very efficiently, masking protein charge states</li><li>Charge envelopes overlap</li><li>Intact mass deconvolution becomes difficult</li><li>PEGylated peptides fragment poorly</li></ul>Traditional approaches like post-column triethylamine (TEA) addition or MALDI have limitations, especially when glycosylation adds another layer of complexity.This is where Orbitrap-based Charge Detection Mass Spectrometry (CD-MS) changes the game.<h3>Step 1: Measuring the intact mass with charge detection MS</h3>The <a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.jproteome.5c00788?goto=supporting-info">team</a> used a <a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/products/560">Thermo Scientific Q Exactive UHMR</a> instrument operating in <a target="_blank" rel="noopener noreferrer" href="https://www.thermofisher.com/content/lifetech/global/en/home/industrial/mass-spectrometry/liquid-chromatography-mass-spectrometry-lc-ms/lc-ms-systems/direct-mass-technology.html">Direct Mass Technology mode</a>.Unlike conventional ensemble MS, CD-MS measures:<ul><li>The m/z of each individual ion</li><li>The charge of each ion directly</li></ul>This enables direct mass determination of highly heterogeneous species.<h5>What did they see?</h5>From the data:<ul><li>Non-PEGylated protein (TP): ~28.95 kDa</li><li>PEGylated protein (PEG-TP): ~58.42 kDa</li></ul>That mass shift strongly supports mono-PEGylation — one PEG per protein molecule.Even more impressively, CD-MS revealed:<ul><li>A minor dimer impurity (~3.7%)</li><li>A small free PEGylation reagent (~30.4 kDa), likely residual reagent</li></ul>The mirror plot (<a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.jproteome.5c00788?goto=supporting-info">Figure 2 on page 4</a>) visually highlights this mass shift, clearly separating the TP and PEG-TP populations.<h4>Why CD-MS was critical</h4>Because PEG is polydisperse, it broadens the mass distribution. In conventional ensemble MS, overlapping charge states prevent proper deconvolution. CD-MS bypasses this by assigning charge per ion, enabling:<ul><li>Accurate intact mass measurement</li><li>Impurity detection</li><li>Quantification</li><li>High reproducibility across runs</li></ul>For complex PEGylated biologics, this represents a major analytical advance.<h3>Step 2: Mapping the pegylation sites (bottom-up strategy)</h3>Knowing there’s one PEG is not enough — regulators and developers need to know where it’s attached.The team designed a multi-enzyme digestion workflow:<ul><li>Lys-C digestion</li><li>Glu-C digestion</li><li>Lys-C/Glu-C combination</li><li>PNGase F treatment to remove N-glycans</li></ul>Each digestion generated peptides of different lengths, providing complementary information.But there was still a problem.PEGylated peptides are difficult to fragment because the large PEG dominates ionization and masks peptide signals.<h3>The clever trick: high source CID</h3>They applied high in-source collision-induced dissociation (~90 eV) to partially strip PEG chains before MS/MS.This generated truncated PEG forms (PEG1–PEG50 variants), allowing:<ul><li>Precursor isolation</li><li>Efficient HCD fragmentation</li><li>Identification of diagnostic fragment ions</li></ul><a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.jproteome.5c00788?goto=supporting-info">Figure 4 (page 7)</a> dramatically shows how high source CID transforms a messy PEG-dominated spectrum into clean multiply charged peptide precursors ready for sequencing.<h3>The result: three pegylation sites identified</h3>Using DDA and software-assisted analysis (<a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/products/1837">Biopharma Finder</a>), the study confidently identified PEGylation at:<ul><li>K52 (major site)</li><li>K45</li><li>N-terminal A1</li></ul>K52 — The dominant site K52 was consistently observed across all digestion strategies. Fragment maps showed strong diagnostic ions carrying truncated PEGs (<a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.jproteome.5c00788?goto=supporting-info">Figures 5–7</a>). Multiple truncations (PEG22–PEG29 and beyond) were observed, confirming robust assignment.K45 — A secondary site K45 was confirmed in the combined Lys-C/Glu-C digestion (<a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.jproteome.5c00788?goto=supporting-info">Figure 8</a>), where shorter peptides improved fragmentation and site localization.N-Terminal A1 — also modified Unexpectedly, PEGylation was also identified at the N-terminus (<a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.jproteome.5c00788?goto=supporting-info">Figure 9</a>), with highly accurate fragment ion mass measurements supporting this assignment.The evidence suggests that:<ul><li>K52 and A1 are the most frequently occupied sites</li><li>K45 is less populated</li></ul><h3>Why this matters for biopharma</h3>PEGylated therapeutics must demonstrate:<ul><li>Batch-to-batch consistency</li><li>Controlled PEGylation stoichiometry</li><li>Clear impurity profiles</li><li>Verified modification sites</li></ul>This workflow delivers:<ul><li>Intact mass confirmation under native condition</li><li>Quantification of impurities</li><li>Confident site localization</li><li>High reproducibility</li><li>Software-assisted interpretation</li></ul>Importantly, it requires minimal sample — a key advantage in early development.<h3>The bigger picture: a blueprint for complex biologics</h3>The combination of:<ul><li>Orbitrap-based Charge Detection MS</li><li>Native intact mass analysis</li><li>Multi-enzyme digestion</li><li>High source CID optimization</li><li>Advanced data processing</li></ul>creates a seamless, comprehensive characterization strategy.Since pharma companies have been adding PEGylated modalities to their pipelines, the importance of this study will continue to shine. Furthermore, PEGylation and other polymer conjugations continue to evolve, and the analytical workflows must keep pace. This study demonstrates how modern mass spectrometry — particularly single-ion charge detection — can tackle extreme molecular heterogeneity with confidence.For PEGylated therapeutics, the mass spectrometer doesn’t just weigh molecules. It tells the full molecular story.<blockquote><h4>Reference:</h4><a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.jproteome.5c00788?goto=supporting-info">Charge Detection Mass Spectrometry and a Glu-C/Lys-C Digestion-Based Data-Dependent Approach Suggest Mono-PEGylation of a Heterogenous Therapeutic Protein</a>Zoltan Szabo, Shero Lao, Katie S. Peterson, Kristina Srzentič, Kyle P. Bowen, Amanda E. Lee, Michael W. Senko, Dietmar Reusch, Steffen Lippold, and Markus HabergerJournal of Proteome Research Article ASAPDOI: 10.1021/acs.jproteome.5c00788</blockquote>Visit us on&nbsp;<a target="_blank" rel="noopener noreferrer" href="https://www.linkedin.com/showcase/72003132/admin/dashboard/">LinkedIn:</a>&nbsp;#PEGylation #Pharmacuetical #teamMassSpec #therapeutics

Cracking the Code of PEGylated Proteins: How Advanced Mass Spectrometry Reveals What’s Really Attached

When test results are used to assess compliance, i.e. to decide whether specifications or regulations are met, the measurement uncertainty of the test results has to be taken into account. Assessment of compliance for cases i and v in the Figure below is clear – the measurement results including the uncertainty interval are clearly above or below the limit value. In the other cases the decision is not clear since the uncertainty interval overlaps the limit value. The Eurachem/CITAC guide [1] gives guidance on cases ii, iii and iv.&nbsp;<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Eurachem_Upper_control_limit_9366d8f597.jpg" alt="Eurachem: Upper control limit" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Eurachem_Upper_control_limit_9366d8f597.jpg 245w," sizes="100vw" width="1536" height="585"><h4>We need acceptance &amp; rejection zones&nbsp;</h4>In order to judge whether the results in cases ii, iii, and iv comply with the limit value we need a decision rule, based on the risks associated with making a wrong decision. This decision rule enables a guard band, g, to be calculated which defines an acceptance zone and a rejection zone. If the measurement value is within the acceptance zone the specifications are met and we can conclude compliance. If the measured value is in the rejection zone, we can conclude non-compliance. The intersection between these two zones is called the decision limit. A guard band is normally chosen so that for a measured value in the acceptance zone the probability of correct acceptance is more than or equal to a defined confidence value α. Note that a guard band, g = 0 can also be used. This is called simple acceptance.&nbsp;<h4>Decision rule&nbsp;</h4>A decision rule should have a well-documented method of determining the location of acceptance and rejection zones, ideally including acceptable levels of probability, P, that the value of the measurand 1) lies within the specification limit, high confidence of correct acceptance (low probability of false acceptance) or 2) lies outside the specification limit, high confidence of correct rejection (low probability of false rejection).<h4>Information needed for assessing compliance&nbsp;</h4>The following information is needed:&nbsp;<ul><li>measurand clearly specified;&nbsp;</li><li>specification stating upper or lower limit or both;&nbsp;</li><li>decision rule;&nbsp;</li><li>measured value:&nbsp;</li><li>measurement uncertainty for a measured value at the limit(s).</li></ul><h4>Example focusing on correct acceptance&nbsp;</h4><ul><li>Measurand: Mass fraction of nickel, Ni in a batch of steel delivered to a customer.&nbsp;</li><li>Uncertainty: U = 0.2 % Ni, k = 2 (95 %). Standard uncertainty, u = 0.1 % Ni. This uncertainty includes both sampling uncertainty for the batch and analytical uncertainty.&nbsp;</li><li>Specification: The specification zone is from the lower limit 16.0 % Ni to the upper limit 18.0 % Ni.&nbsp;</li><li>Decision rule High confidence of correct acceptance: The acceptance range is the mass fraction where it can be decided with a confidence level of approximately 95 % (α = 0.05) that the batch has a mass fraction above the lower limit and below the upper limit.&nbsp;</li><li>Guard band: Each guard band is calculated as 1.64u ≈ 0.17 % (rounded upward for safety) with k value 1.64 from the one-tailed upper 95 % quantile of the normal distribution.&nbsp;</li><li>Acceptance zone: 16.2 % Ni to 17.8 % Ni , after rounding to one decimal place.&nbsp;</li><li>Measured value: 16.1 % Ni</li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Eurachem_Guard_bands_g_and_acceptance_and_a_rejection_zones_based_on_a_lower_and_upper_bedc4769b3.jpg" alt="Eurachem: Guard bands (g), and acceptance and a rejection zones based on a lower and upper limit and a decision rule stating high confidence of correct acceptance" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Eurachem_Guard_bands_g_and_acceptance_and_a_rejection_zones_based_on_a_lower_and_upper_bedc4769b3.jpg 245w," sizes="100vw" width="1091" height="447">The measured value, 16.1 % Ni, is below the lower acceptance limit of 16.2 %; that is, in the rejection zone. The batch is non-compliant.&nbsp;<blockquote>Note – if the decision rule stated simple acceptance the acceptance zone would be 16.0 % to 18.0 % and the batch would be compliant.&nbsp;</blockquote><h4>Example focusing on correct rejection&nbsp;</h4><ul><li>Measurand: Mass fraction of a banned substance in a sample.&nbsp;</li><li>Uncertainty: The relative standard uncertainty urel is 35 %.&nbsp;</li><li>Specification: Upper limit is 2 ng/g.&nbsp;</li><li>Decision rule High confidence of correct rejection: The concentration of the banned substance will be deemed to be above the limit if the probability of the value of the concentration being greater than the limit is 95 % or greater.</li><li>Guard band: The guard band g for correct rejection is 1.6 ng/g assuming a lognormal distribution (due to the high relative uncertainty – see further Guide Annex A, Case 4 [1]).&nbsp;</li><li>Acceptance limit: 3.6 ng/g&nbsp;</li><li>Measured value: 3.3 ng/g&nbsp;</li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Eurachem_Guard_band_g_and_acceptance_and_a_rejection_zones_based_f0f8f140db.jpg" alt="Eurachem: Guard band (g), and acceptance and a rejection zones based on a decision rule stating high confidence of correct rejection" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Eurachem_Guard_band_g_and_acceptance_and_a_rejection_zones_based_f0f8f140db.jpg 245w," sizes="100vw" width="883" height="392">The measured value, 3.3 ng/g, is below the acceptance limit of 3.6 ng/g; that is, in the acceptance zone. The sample is compliant. Note that the assumption of the type of distribution is crucial. If assuming a normal distribution in this case the acceptance limit would be 3.2 ng/g and the sample would not be compliant.

Use of uncertainty in compliance

<h3><a target="_blank" rel="noopener noreferrer" href="https://www.isc2026.org/">ISC 2026</a></h3>The <a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/companies/314">International Symposium on Chromatography (ISC)</a> represents the oldest conference series on separation science. ISC symposia have been organised since 1956 in each even year. ISC is one of the premier meetings series for discussion of all modes of chromatography and separation science with a broad coverage of techniques and applications.<h4>35th International Symposium on Chromatography</h4>📆6. - 10. September 2026📍Prague, Czech Republic<h3>REGISTRATION</h3><blockquote>👉<a target="_blank" rel="noopener noreferrer" href="https://www.czech-in.org/cmPortalV15/Account/Login?ReturnUrl=%2FcmPortalV15%2FPortal%2FISC26%2Fnormal">Register HERE for the ISC 2026</a>Late Registration until 25 August 2026</blockquote><h3>ABSTRACT SUBMISSION</h3>There is still an opportunity to share your latest results at ISC 2026!&nbsp;<blockquote>👉<a target="_blank" rel="noopener noreferrer" href="https://www.czech-in.org/cmPortalV15/Account/Login?ReturnUrl=%2FcmPortalV15%2FPortal%2FISC26%2Fnormal">Submit your Abstract HERE</a><ul><li>Deadline for late-breaking poster abstract submission: July 30, 2026&nbsp;</li><li>Please note that late-breaking posters cannot compete for the Best Poster Award.&nbsp;</li></ul></blockquote><h3>ISC TUBE 2026</h3>Since its launch in 2019, Tube has become a beloved highlight of chromatography conferences — offering scientists a fun, creative outlet to express their passion for separation science. At ISC 2026, the excitement continues in Prague, and the top three videos will be awarded. Open to individuals and groups of all ages, the winners will be determined live by electronic audience voting.&nbsp;We invite you to create a short video (up to 1 minute) showing why you love chromatography! No need for fancy editing — just grab your phone and let your imagination flow. Be funny, be inspiring, be dramatic — but most importantly, be yourself! This is not a scientific presentation — it’s a science show! Your mission is to bring chromatography closer to the ISC audience in an engaging and entertaining way.<blockquote>👉<a target="_blank" rel="noopener noreferrer" href="https://files.c-in.eu/s/S7ekt8FYygFBNEW">UPLOAD YOUR VIDEO HERE</a></blockquote><h4>Rules for Participation</h4><ol><li>Format: Typical video formats, such as MP4, MPG, AVI, and others.&nbsp;</li><li>The theme is broad, but here are a few ideas to spark your creativity:</li></ol><ul><li>Infomercial: Combine science and storytelling — sell us your chromatography as if it’s changing the world!&nbsp;</li><li>Sports Highlights: Recreate your lab’s “winning moment” — a slam dunk analysis or record-breaking run time.&nbsp;</li><li>Movie Trailer: Turn your chromatography into a blockbuster — dramatic voiceovers encouraged!</li></ul><ol><li>Content: Make your video engaging, persuasive, and visually appealing. Showcase your research and chromatographic practice with flair.&nbsp;</li><li>Creativity: Think about what captivates you — a sports replay, a movie trailer, or even a teleshopping ad. Now channel that energy into your chromatography story!&nbsp;</li><li>Deadline: Upload your video via <a target="_blank" rel="noopener noreferrer" href="https://files.c-in.eu/s/S7ekt8FYygFBNEW">file upload</a> by July 31st 2026. In case you have questions please refer to plachkka@faf.cuni.cz.</li></ol><h4>Evaluation Criteria</h4><ul><li>Winners will be selected via live electronic audience voting</li><li>Judging will be based on scientific relevance, creativity, entertainment value, and technical quality</li><li>Entries containing discriminatory or offensive content will be excluded</li></ul><h4>Who Can Participate?</h4><ul><li>Eligibility: Scientists (academic or industrial) of any age registered for the ISC 2026 and working on chromatography-related projects — before, during, or after the separation step</li><li>Submissions: Individual and group entries are welcome&nbsp;</li><li>Content: Videos must be based on the participant’s own work&nbsp;</li><li>Selection: A shortlist of top videos will be chosen for the live finals at ISC 2026, which will be held on Tuesday 8 September, 18:30 – 19:30&nbsp;</li></ul>

ISC 2026 - ISC Tube & Late-Breaking Poster Deadline

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The International Symposium on Chromatography (ISC) represents the oldest conference series focussing on separation science. ISC symposia have been organised since 1956 in each even year. ISC is internationally recognised as one of the premier meeting series for discussion of all modes of chromatography and separation science with a broad coverage of techniques and applications.

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Cracking the Code of PEGylated Proteins: How Advanced Mass Spectrometry Reveals What’s Really Attached

ISC 2026 - ISC Tube & Late-Breaking Poster Deadline

Use of uncertainty in compliance