Ligandability Mapping Service

Evaluate whether difficult targets, protein sites, or reactive residues can be engaged by small molecules, fragments, or covalent probes.

Ligandability mapping helps discovery teams evaluate whether difficult targets, protein sites, or reactive residues can be engaged by small molecules, fragments, or covalent probes. At Creative Proteomics, we combine MS-based chemoproteomics, ABPP, structural MS, and binding evidence to prioritize ligandable opportunities and guide follow-up discovery decisions.

Key Advantages:

Map ligandable sites and binding hotspots.
Prioritize reactive residues and target regions.
Support difficult-target hit discovery.
Connect weak hits with site evidence.
Receive review-ready data deliverables.

Discuss Your Mapping Project

Ligandability mapping service overview showing difficult targets, sample types, MS workflows, hotspot maps, and evidence outputs.

Mapping Capabilities Use Cases Workflow Sample Demo Results Deliverables Comparison Strategy Literature FAQ References Disclaimer

Ligandability Mapping for Difficult Targets and Binding-Site Discovery

Many discovery programs begin with a biologically important target, but the next question is often harder: can the target be engaged by a useful small molecule, fragment, probe, or covalent ligand? Ligandability mapping is designed to answer this early question with experimental evidence.

Our ligandability mapping service helps you evaluate whether a target, protein region, reactive residue, or binding hotspot shows evidence of ligand engagement. Instead of relying only on a predicted pocket or a single assay readout, we use MS-based approaches to build a practical evidence map around the target.

This service is especially useful for difficult targets, protein complexes, targets without mature functional assays, reactive residue discovery, fragment-based programs, and covalent ligand discovery.

What Ligandability Mapping Can Reveal

A well-designed ligandability mapping study can help answer several practical questions:

Does the target contain a site that can be engaged by a ligand?
Are there reactive residues that may support covalent ligand discovery?
Can weak fragments or early hits be connected to a binding region?
Is the evidence protein-level only, or does it support a specific peptide, residue, or hotspot?
Which method is most appropriate: ABPP, reactive residue profiling, ASMS, HDX-MS, thermal profiling, or another MS-based strategy?
Which sites or target regions should be prioritized for follow-up screening or validation?

For many teams, the most useful output is not simply a list of proteins. It is a ranked view of ligandable opportunities, evidence strength, sample context, and next-step recommendations.

Ligandability Is Not the Same as Druggability

Ligandability and druggability are related, but they are not the same. Ligandability asks whether a site, protein region, or target can be engaged by a ligand. Druggability requires additional downstream evidence, such as potency, selectivity, cellular activity, functional relevance, and developability.

We treat ligandability mapping as an early evidence layer. It can help your team decide whether a target is worth deeper screening, which site or region deserves attention, and which follow-up method should come next. It does not replace later optimization or functional validation, but it can reduce uncertainty before larger discovery investments.

Our Ligandability Mapping Capabilities

We designed our ligandability mapping service for discovery teams that need experimental guidance before committing to large-scale screening or optimization. We help evaluate target fit, select an appropriate MS-based strategy, process samples, and organize results into a review-ready evidence package.

MODE 1

Chemoproteomic Ligandable Site Mapping

Chemoproteomic ligandability mapping can help identify probe-accessible or ligand-engaged sites across a target, protein family, or sample system. Depending on the design, this may involve activity-based protein profiling, competitive chemoproteomics, enrichment-based workflows, or residue-focused LC-MS/MS analysis.

This approach is useful when your team wants to understand whether a protein site can be chemically engaged in a native or near-native biological context.

For method context, see our Activity-Based Protein Profiling (ABPP-MS) service.

MODE 2

Reactive Residue and Hotspot Prioritization

Reactive residues can provide important entry points for ligand discovery, especially in covalent ligand programs. A residue may be interesting because it is accessible, chemically reactive, functionally relevant, or repeatedly engaged across compounds.

We can help prioritize reactive residue candidates and hotspot regions where the workflow supports peptide- or site-level evidence. These outputs may support covalent fragment screening, analog design, target engagement studies, or follow-up validation.

For residue-focused projects, see our Reactive Residue Profiling service.

MODE 3

Fragment and Compound Engagement Evidence

Some projects begin with weak binders, fragment hits, or a small compound set. Ligandability mapping can help connect these early signals to a target region or site hypothesis. Depending on the sample system and compound type, this may involve ASMS, chemoproteomics, thermal profiling, pull-down strategies, or structural MS.

This is useful when a fragment or weak hit has potential, but the binding context is unclear. A mapping workflow can help decide whether the signal deserves deeper screening or whether another method is needed.

MODE 4

Structural and Conformational Evidence

Binding may not always produce a direct site-level chemical label. In those cases, structural MS methods can add complementary evidence. HDX-MS, footprinting, thermal stability profiling, or related MS-based approaches can help detect binding-region protection, conformational shifts, or stability changes.

These methods can be especially useful when the target has limited structural information, flexible regions, protein-protein interaction interfaces, or conformational states that are difficult to study with one technique alone.

MODE 5

Multi-Method Evidence Matrix

Difficult targets often need more than one type of evidence. We can combine results from chemoproteomics, ABPP, ASMS, HDX-MS, thermal profiling, pull-down studies, or biophysical follow-up into a clear evidence matrix.

This matrix can help your team see which sites have the strongest support, which findings are exploratory, and which next steps are most appropriate.

When to Use Ligandability Mapping

Ligandability mapping is most valuable when a target is biologically compelling but the path to hit discovery is uncertain.

When a Target Looks Important but Hard to Drug

Some targets are important because of disease biology, pathway position, or genetic evidence, but they do not offer an obvious active site or standard functional assay. These may include scaffold proteins, transcription factors, protein complexes, protein-protein interaction targets, or membrane-associated proteins.

Ligandability mapping can help determine whether the target contains a site, region, or residue that can be experimentally engaged. This can give your team a more practical basis for deciding whether to proceed with screening.

When Functional Assays Are Not Ready

A target may be promising before a robust functional assay exists. In this situation, MS-based ligandability evidence can provide an entry point before traditional high-throughput screening is available.

For example, ASMS may support direct binding discovery with purified protein, while ABPP or chemoproteomics may help identify probe-accessible or reactive sites in lysates or cells. Structural MS can add evidence when binding or conformational changes are more important than a direct functional readout.

When Weak Hits Need Binding-Site Context

Weak hits are common in early fragment or small-molecule discovery. The challenge is deciding which signals are worth investment. Ligandability mapping can help connect weak hit engagement to a protein region, residue, or method-supported hotspot.

This can help your team decide whether to expand a fragment series, redesign a compound, test a covalent analog, or move to orthogonal validation.

When Covalent Ligand Discovery Needs Reactive Site Priority

Covalent ligand discovery depends on identifying chemically addressable residues that can be engaged with useful selectivity. A reactive residue alone is not enough. It must be evaluated in context: accessibility, engagement evidence, protein function, site uniqueness, and follow-up feasibility all matter.

Ligandability mapping can help prioritize reactive sites before deeper covalent fragment screening or analog optimization. For upstream covalent screening, see our Covalent Fragment Screening service.

Workflow with QC Checkpoints from Target Intake to Mapping Report

Our workflow follows the target, sample, or compound from initial review to final evidence delivery. Each stage combines technical execution with QC review so that the final report is grounded in target biology, sample quality, method fit, and MS data quality.

Target, Sample, and Method Fit Review

We review your target, sample type, biological question, available structure information, compound or fragment availability, probe options, and expected decision point.

Strategy Selection

After reviewing the project goal, we help select the most suitable mapping strategy, such as chemoproteomics, ABPP, ASMS, HDX-MS, thermal profiling, pull-down chemoproteomics, or a combined approach.

Sample Preparation and Treatment Design

Samples may include purified recombinant proteins, protein complexes, cell lysates, live cells, tissue lysates, fragments, compounds, or probes. The preparation plan depends on the selected method.

MS-Based Acquisition and Mapping

ABPP or chemoproteomics may involve labeling, enrichment, digestion, and LC-MS/MS analysis. ASMS may evaluate compound binding to a purified target. HDX-MS or footprinting may capture region-level protection or conformational changes. Thermal profiling may detect stability shifts after ligand exposure.

Data Filtering, QC, and Evidence Ranking

After acquisition and processing, we review the data for quality and interpretability, including protein and peptide confidence, replicate consistency, background signal, enrichment behavior, coverage, missing values, and method agreement.

Final Ligandability Report

The final report may include ranked ligandable sites, reactive residue candidates, binding hotspot summaries, fragment engagement results, method evidence matrices, QC notes, and recommended next steps.

Vertical ligandability mapping workflow with QC checkpoints from target intake to final evidence report.

The report should help your team decide which sites or regions deserve follow-up, which method produced the strongest evidence, which results are exploratory, which target or sample format should be tested next, and whether the project should move into fragment screening, covalent ligand discovery, validation, or additional structural analysis.

Sample Requirements and Project Intake Checklist

Sample requirements depend on the selected mapping strategy. The table below gives reference planning guidance for common project inputs. Final design should be reviewed before sample preparation.

Sample / Input Type	Recommended Amount / Format	Required Information	Best-Fit Use	QC Checkpoints	Notes
Cultured cells	Reference planning range: 5 × 10⁶ cells for label-free quantitative proteomics; 1 × 10⁷ cells for DIA-style quantitative proteomics	Cell line, treatment condition, biological question, target context, controls	Live-cell ligandability or chemoproteomic mapping	Cell pellet consistency, treatment consistency, labeling or enrichment performance	Cell samples should be washed with pre-chilled PBS, flash-frozen, stored at −80°C, and shipped with dry ice where applicable
Purified recombinant protein	Project-dependent; provide concentration, buffer, purity, and stability details	Sequence, tag, construct boundaries, buffer, known ligands, structure availability	ASMS, HDX-MS, footprinting, SPR, ITC, or BLI follow-up	Protein integrity, aggregation risk, buffer compatibility	Technical review is recommended before shipment
Protein complex	Project-dependent; provide stoichiometry and stability information	Complex components, assembly method, buffer, cofactors, known interaction partners	Binding hotspot or conformational mapping	Complex integrity, sample homogeneity, MS compatibility	Stability and buffer review are important
Cell lysate	Reference planning follows quantitative proteomics input when applicable	Species, cell type, lysis condition, treatment design, protein concentration	Controlled chemoproteomic ligandability mapping	Protein quality, buffer compatibility, labeling or enrichment behavior	Avoid incompatible detergents or additives where possible
Tissue lysate	Reference planning range: soft animal tissue 100 mg for label-free quantitative proteomics and 200 mg for DIA-style quantitative proteomics	Tissue type, group design, storage condition, model or treatment context	Tissue-context ligandability or reactive site mapping	Sample integrity, heterogeneity, protein recovery	Samples should be flash-frozen and protected from repeated freeze-thaw cycles
Fragment or compound library	Compound list, structures if available, solvent, stock concentration, purity notes	Compound IDs, grouping, known targets, solubility, reactive groups if present	Fragment engagement or covalent ligand discovery support	Compound fit, solubility, control design	Library format should be reviewed before project start
Activity-based probe or clickable ligand	Probe class, handle, target class, storage notes	Probe structure, supplier or synthesis information, expected labeling space	ABPP or chemoproteomic enrichment	Probe control, background signal, enrichment performance	Probe choice defines measurable chemical space

Before submission, please prepare the target name, protein sequence, construct, or sample context; available structural information, if any; sample type and storage condition; compounds, fragments, probes, or known ligands; desired biological question; control groups and comparison groups; known buffer, solubility, stability, or aggregation concerns; and preferred follow-up direction, such as fragment screening, covalent ligand discovery, or structural validation.

Representative Demo Results for Ligandability Mapping

Representative outputs should help your team understand where the strongest ligandability evidence is located and how each finding can be used. We usually organize results around site visualization, ranked residue evidence, and cross-method support.

Representative ligandability mapping demo results with hotspot map, reactive residue table, and multi-method evidence matrix.

Representative ligandability mapping outputs

Demo 1: Ligandable Hotspot Map

A ligandable hotspot map can show a protein domain, surface region, or target region with highlighted sites. These sites may represent reactive residues, fragment-engaged regions, protected peptide regions, or regions supported by more than one method.

Review which region of the target appears most actionable.
Assess whether the evidence is localized or broad.
Connect sites to known domains, interfaces, or functional regions.
Prioritize hotspots for follow-up testing.

Demo 2: Reactive Residue Priority Table

A reactive residue priority table can rank sites by evidence type, engagement signal, method support, and follow-up priority. Where supported, the table may include peptide-level evidence and residue annotation.

Identify promising reactive residues.
Review which sites are supported by stronger evidence.
Separate exploratory sites from higher-priority sites.
Support covalent ligand discovery decisions.

Demo 3: Multi-Method Evidence Matrix

A multi-method evidence matrix can compare results from ABPP, ASMS, HDX-MS, thermal profiling, pull-down, or other selected methods. This gives your team a clearer view of how different evidence types support the same site, region, or target.

Review whether multiple methods support the same region.
Clarify whether evidence is direct, indirect, or exploratory.
Decide which method should be used next.
Identify sites or regions ready for follow-up validation.

Bioinformatics Analysis and Deliverables

Ligandability mapping can generate different data types depending on the selected method. We organize the results so they can be reviewed internally and used for follow-up decisions.

Deliverable	What It Helps You Review
Raw LC-MS/MS files, where applicable	Primary data archive and reanalysis support
Search result files	Protein, peptide, or site identification review
Protein-level quantified table	Target and sample-level evidence overview
Peptide / residue-level evidence table, where supported	Site-level interpretation
Ranked ligandable site or hotspot list	Prioritized follow-up planning
Reactive residue candidate table	Covalent ligand discovery support
Compound or fragment engagement summary, where included	Weak-hit or fragment interpretation
QC summary	Data quality, controls, and replicate behavior
Methods and parameter summary	Traceability of acquisition and analysis settings
Visualization-ready figures	Internal presentation and scientific review

Optional add-ons may include domain or structural annotation, protein family annotation, pathway or target-class context, residue class summary, ligandability evidence scoring, cross-method evidence matrices, orthogonal validation recommendations, and custom filtering by site confidence or follow-up priority.
Depending on the evidence pattern, results may support fragment screening expansion, covalent ligand discovery, reactive residue validation, structural follow-up, thermal profiling, pull-down studies, biophysical validation, or functional assay development.
For related proteome-wide ABPP outputs, see Global ABPP (LC-MS/MS).

Ligandability Mapping vs Other Discovery Methods

Different discovery methods answer different questions. Ligandability mapping is most useful when your team needs experimental evidence that a target, site, residue, or region can be engaged by a ligand. Orthogonal methods can then support direct binding, structural interpretation, cellular engagement, or functional follow-up.

Method	Best-Fit Question	Sample Context	Requires Known Structure?	Requires Compound or Probe?	Site-Level Evidence Potential	Proteome-Wide Capability	Best Output	Key Limitation	Best Follow-Up Use
Chemoproteomic ligandability mapping / ABPP	Which reactive or probe-accessible sites can be engaged?	Cells, lysates, tissues, or protein systems depending on design	Not always required	Usually requires probe, ligand, or reactive chemistry	Strong where peptide/site evidence is captured	Strong in suitable workflows	Ranked site or protein evidence	Limited to measurable chemical space	Reactive site prioritization and covalent ligand discovery
Reactive residue profiling	Which residues are chemically addressable?	Cells, lysates, tissues, or proteins	Not required	Requires residue-focused chemistry or probe strategy	Strong	Moderate to strong	Reactive residue table	Does not always prove functional relevance	Site validation and covalent ligand design
ASMS / fragment screening	Which fragments bind a purified target?	Purified protein or protein complex	Helpful but not always required	Requires compound or fragment library	Usually low unless paired with mapping	Usually target-focused	Binder list	Binding site may remain unclear	Hit discovery and follow-up mapping
HDX-MS / footprinting / structural MS	Which region changes after ligand binding?	Purified proteins or complexes	Structure helps interpretation but may not be required	Requires ligand, fragment, or condition comparison	Region-level evidence	Target-focused	Protected regions or conformational map	Requires careful protein quality and coverage	Structural interpretation and binding region validation
Thermal stability profiling	Which proteins show stability shifts after ligand treatment?	Cells, lysates, or proteins	Not required	Requires ligand or compound treatment	Usually protein-level	Strong in proteome-wide formats	Stability-shift evidence	Not all binding causes stability change	Orthogonal engagement support
Pull-down chemoproteomics	Which proteins are enriched by a ligand or probe?	Cells, lysates, or enriched systems	Not required	Usually requires tagged or clickable ligand	Sometimes	Strong depending on design	Enriched target list	Probe modification may affect binding	Target ID and binder confirmation
SPR / ITC / BLI	What is the affinity, kinetics, or thermodynamics?	Purified target	Not required	Requires purified target and ligand	No proteome-wide site map	Low	Binding constants or kinetic data	Not global and requires purified protein	Biophysical validation
Structure-based virtual screening	Which compounds fit a predicted or known pocket?	Computational model or structure	Yes, strongly preferred	Requires compound library	Pocket-level prediction	Depends on model	Ranked virtual hits	Prediction needs experimental confirmation	Experimental screening and validation

How to Choose the Right Ligandability Mapping Strategy

Choose Chemoproteomics When Reactive or Probe-Accessible Sites Matter

Chemoproteomics or ABPP is a strong fit when the question is centered on reactive residues, covalent ligand opportunities, or probe-accessible protein sites. This is especially useful when your team wants to explore cysteine, lysine, serine, or other chemically addressable residue classes.

The project needs site or residue-level evidence.
A probe or reactive ligand strategy is available.
Covalent ligand discovery is a likely next step.
Native sample context matters.

Choose ASMS or Fragment Screening When Direct Binding Is the First Question

ASMS and fragment screening are useful when your team has purified protein and wants to identify direct binders. These methods can be especially helpful before deeper site mapping.

A purified target or protein complex is available.
A fragment or compound library is ready.
The first goal is binding discovery.
The binding site can be mapped later by structural MS or chemoproteomics.

For direct binding projects, see Affinity Selection Mass Spectrometry (ASMS).

Choose HDX-MS or Footprinting When Structural Context Matters

HDX-MS, footprinting, and related structural MS methods are useful when your team needs region-level evidence or conformational insight. These methods can help when binding changes protein dynamics, protects a region, or shifts conformational behavior.

The binding region is unknown.
A ligand or fragment has weak but reproducible binding.
Protein conformation matters.
Structural models need experimental support.

Combine Methods When One Evidence Type Is Not Enough

Difficult targets often require multiple evidence layers. A combined strategy may be useful when one method gives a weak but interesting signal, when the target lacks structural information, or when a project decision depends on stronger support.

ABPP plus reactive residue profiling.
ASMS plus HDX-MS.
Chemoproteomics plus thermal stability profiling.
Pull-down chemoproteomics plus site-level LC-MS/MS.
Ligandability mapping followed by Covalent Inhibitor Profiling.

For probe-accessible engagement studies, see our Competitive ABPP service. For orthogonal stability-shift evidence, see Proteome-wide Thermal Stability Profiling.

Literature Sources for Ligandability Mapping Evidence

Background

Proteome-wide ligandability mapping is valuable because many small molecules engage more than one protein, and many promising targets lack obvious binding pockets. Mapping ligand engagement across native biological systems can help reveal hotspot residues, candidate protein targets, and difficult-to-address protein categories.

Source for Verification

The study Proteome-wide ligandability maps of drugs with diverse cysteine-reactive chemotypes reports proteome-wide cysteine ligandability maps for drugs with diverse cysteine-reactive chemotypes. It provides useful literature support for ligandability mapping, reactive cysteine engagement, hotspot analysis, and functional categorization of engaged proteins.

Figure Reference for Review

Figure 3 in the paper reports cell-based profiling of drug-engaged cysteines, including hotspot cysteine patterns, protein target categories, and functional annotation of DrugBank and non-DrugBank proteins. This figure can be reviewed from the original source page. For page artwork, an original schematic should be created instead of reusing or adapting the published figure.

Additional Literature for Method Context

Original ligandability mapping schematic showing drug-engaged cysteine hotspots and functional protein target categories.

Original schematic for ligandability mapping evidence. Published figures should be reviewed from the source article rather than reused without permission.

FAQ

Frequently Asked Questions

Q: What is ligandability mapping?

Ligandability mapping is an experimental strategy for evaluating whether a protein, site, residue, or region can be engaged by a small molecule, fragment, probe, or covalent ligand. It can help prioritize targets and sites before larger screening or optimization programs.

Q: How is ligandability different from druggability?

Ligandability asks whether a target or site can be engaged by a ligand. Druggability requires additional evidence, including potency, selectivity, cellular activity, functional relevance, and development potential. Ligandability mapping is an early evidence layer, not a final druggability claim.

Q: Do I need a crystal or Cryo-EM structure before starting?

Not always. Structural information can help with interpretation, but ligandability mapping can also use chemoproteomics, ABPP, ASMS, HDX-MS, footprinting, thermal profiling, or pull-down approaches when high-resolution structure is unavailable.

Q: Can ligandability mapping support difficult targets?

Yes. It is especially useful for targets that lack mature functional assays, obvious binding pockets, or complete structural information. The goal is to identify experimental evidence of ligandable sites, binding hotspots, or reactive residues that can support follow-up discovery.

Q: Which sample types are compatible?

Common inputs may include purified recombinant proteins, protein complexes, cell lysates, live cells, tissue lysates, fragment libraries, compounds, activity-based probes, or clickable ligands. Final feasibility depends on target type, sample quality, method selection, and project goals.

Q: When should I choose ABPP or reactive residue profiling?

Choose ABPP or reactive residue profiling when the project focuses on probe-accessible targets, reactive residues, covalent ligand opportunities, or site-level chemoproteomic evidence. These methods are useful when chemical engagement can be captured by labeling or enrichment.

Q: When should I choose ASMS or fragment screening?

Choose ASMS or fragment screening when direct binding is the first question and purified protein or protein complex is available. These approaches can identify binders that may later be evaluated with structural MS, chemoproteomics, or functional assays.

Q: Can the workflow provide site-level evidence?

Site-level evidence may be available when the selected method, sample quality, peptide coverage, and LC-MS/MS data support it. We identify whether each result is protein-level, peptide-level, residue-level, or region-level where possible.

Q: What data deliverables will we receive?

Typical deliverables may include raw LC-MS/MS files where applicable, search result files, protein-level tables, peptide or residue-level evidence where supported, ranked ligandable site lists, reactive residue tables, QC summaries, methods notes, and visualization-ready figures.

Q: How can ligandability mapping guide follow-up discovery?

Ligandability mapping can help prioritize targets, residues, hotspots, fragments, or protein regions for follow-up work. Results may guide fragment screening, covalent ligand discovery, HDX-MS validation, thermal profiling, pull-down studies, biophysical assays, or functional assay development.

References

Compliance Disclaimer

This service is provided for Research Use Only.

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