Nucleotide Detection Panel — 30+ Analytes Across Purine, Pyrimidine & Cyclic Nucleotide Metabolism

Nucleotides are quantified by HILIC LC-MS/MS on a SCIEX QTRAP 6500+ with stable isotope internal standards for each class. The panel is organized by nucleobase and phosphorylation state because the ratios — not individual concentrations — are the biologically informative readout. Energy charge (AEC), ATP/ADP ratio, UTP/CTP balance, and cAMP/cGMP levels each answer a different biological question. For purine-specific profiling, see our purine metabolism panel; for pyrimidine-focused analysis, our pyrimidine metabolism service covers UTP, CTP, TTP, and their degradation products.

Adenylates — ATP, ADP, AMP & Energy Charge

Metabolite	Phosphorylation	Key Ratio & Biological Significance
ATP	Triphosphate	Adenylate Energy Charge (AEC) = (ATP + 0.5 ADP) / (ATP + ADP + AMP). Ranges from 0 (all AMP) to 1.0 (all ATP). Healthy cells: 0.85-0.95; metabolic stress: below 0.7. More informative than ATP alone — integrates all three phosphorylation states into a single functional index of cellular energy status.
ADP	Diphosphate	ATP/ADP ratio — direct readout of oxidative phosphorylation and glycolytic ATP production. ATP/ADP drops within seconds of hypoxia or mitochondrial inhibition. Note: a fraction of ATP fragments to ADP in the MS ion source — corrected using 13C10-ATP IS to subtract the fragmentation contribution from true ADP. Paired with AEC, distinguishes ATP consumption from ATP production failure.
AMP	Monophosphate	AMP/ATP ratio — activates AMPK when elevated. AMP is normally kept very low by adenylate kinase (2 ADP ↔ ATP + AMP). Elevated AMP signals energetic crisis and triggers catabolic reprogramming via AMPK.

Guanylates, Uridylates & Cytidylates

Metabolite Class	Species	Key Ratio & Biological Significance
Guanylates	GTP, GDP, GMP	GTP/GDP ratio — GTP is the primary energy currency for protein synthesis (translation initiation and elongation), G-protein signaling, and microtubule polymerization. GTP/GDP ratio reflects the balance of TCA cycle-derived GTP synthesis vs. macromolecular biosynthesis consumption. Depleted in rapidly proliferating cells with high translational demand.
Uridylates	UTP, UDP, UMP, UDP-glucose, UDP-GlcNAc	UTP/UDP ratio — UTP is the RNA synthesis substrate, UDP-glucose feeds glycogen synthesis, and UDP-GlcNAc drives protein glycosylation. UDP-sugar species link nucleotide metabolism to carbohydrate and glycan pathways.
Cytidylates	CTP, CDP, CMP	CTP/UTP ratio — CTP is synthesized from UTP by CTP synthetase, the rate-limiting step for phospholipid synthesis (CTP + phosphocholine → CDP-choline). CTP/UTP ratio reflects CTP synthetase activity and membrane lipid biosynthetic demand.

Cyclic Nucleotides, Deoxynucleotides & Purine Degradation

Metabolite Class	Species	Key Ratio & Biological Significance
Cyclic Nucleotides	cAMP, cGMP, cGAMP (2'3'-cGAMP)	cAMP: canonical GPCR second messenger — adenylyl cyclase converts ATP→cAMP, activating PKA and CREB-mediated transcription. cGMP: guanylyl cyclase second messenger for NO signaling and photoreception. cGAMP (2'3'-cGAMP): produced by cGAS upon cytosolic DNA sensing, activates STING — central to innate immunity, autoimmunity, and cancer immunotherapy.
Deoxynucleotides	dATP, dGTP, dCTP, dTTP	dNTP/NTP ratio — dNTP pools are cell-cycle regulated (peak in S phase) at much lower concentrations than ribonucleotides. dNTP imbalance causes replication stress and mutagenesis. Chromatographic separation from ribonucleotides is essential — ATP and dGTP share identical nominal mass.
Purine Degradation	Inosine, hypoxanthine, xanthine, uric acid	Uric acid/xanthine ratio — reflects xanthine oxidase activity at the terminal step of purine catabolism. Allantoin (further oxidized uric acid) measured in uricase-expressing species (rodents). Purine degradation products are the most stable nucleotide analytes during sample handling.

HILIC LC-MS/MS Platform for Nucleotide Quantification

LC-MS/MS Platform

SCIEX QTRAP 6500+ with scheduled MRM acquisition. HILIC chromatography (Waters XBridge BEH Amide, 2.1 × 100 mm, 3.5 um) for retention of highly polar phosphorylated nucleotides — reversed-phase C18 alone provides insufficient retention for ATP, GTP, and other triphosphates. Ammonium formate/acetonitrile gradient with metal-chelating additive (EDTA or methylene phosphonic acid) to prevent peak tailing from nucleotide-metal ion interactions.

Stable isotope internal standards: 13C10-ATP, 13C10-ADP, 13C10-AMP, 13C10-GTP, 13C9-UTP, 13C9-CTP, d3-cAMP, d3-cGMP. Ion-pairing chromatography (dibutylammonium acetate) available as complementary method for challenging isomer separations (ATP vs dGTP share identical nominal mass).

Method Performance

Parameter	Specification
LOD	0.1-5.0 ng/mL (species-dependent); ATP: 0.5 ng/mL, cAMP: 0.1 ng/mL, cGAMP: 0.05 ng/mL
Linear Range	3-4 orders of magnitude; R2 above or equal to 0.995 per analyte
Quantification	Absolute — stable isotope dilution with 6-point calibration, 1/x2 weighted regression
Precision (CV)	Intra-batch: below 5% (ATP, ADP, AMP), below 10% (cyclic). Inter-batch: below 15%
Spike Recovery	85-115% at low/mid/high QC levels

Nucleotide Analysis Workflow — From Quenching to Energy Charge

Phosphatase-Inhibited Quenching

Cell pellets: ice-cold perchloric acid (0.5 M) or acetonitrile:methanol:water (40:40:20) added within 1 second of harvest. Tissue: freeze-clamp with liquid N2-cooled Wollenberger tongs. Plasma: EDTA with sodium fluoride (phosphatase inhibitor), separated and frozen within 15 min. All samples on dry ice.

Neutralization & Extraction

Acid-quenched extracts neutralized with KOH/K2CO3 to pH 6.5-7.0. Stable isotope IS cocktail added. Centrifugation to remove precipitated salts and proteins. For tissue: homogenization in acid followed by neutralization. dNTP pool stabilization with additional antioxidant (ascorbic acid).

HILIC LC-MS/MS Acquisition

HILIC separation (Waters XBridge BEH Amide) with ammonium formate/acetonitrile + EDTA gradient — EDTA chelates metals that cause nucleotide peak tailing. Scheduled MRM, 2-3 transitions per analyte. Sequence: blank, 6 calibrators, 3-level QC, randomized samples with QC every 8-10 injections.

Quantification & AEC Calculation

Stable isotope dilution with 1/x2 weighted calibration. AEC = (ATP + 0.5 ADP)/(ATP + ADP + AMP) calculated per sample. ATP/ADP, GTP/GDP, UTP/CTP ratios included. Pooled QC AEC tracked across batch — any drift flagged as system suitability alert.

Report Delivery

Concentration table (nmol/mg protein, nmol/10^6 cells, or uM) per analyte. Pre-calculated AEC and nucleotide ratios. MRM chromatograms with IS overlay. QC report. Methods documentation.

Nucleotide Analysis Workflow — Five-Step Pipeline from Acid Quenching to Energy Charge Report

Sample Types & Collection for Nucleotide Analysis

Sample Type	Minimum Amount	Critical Handling	Storage & Shipping
Cell Pellet	1-5 x 10^6 cells	Ice-cold PBS wash, aspirate completely. Quench with ice-cold perchloric acid or acetonitrile:methanol:water within 1 sec of harvest. ATP/ADP/AMP interconversion begins immediately upon cell disruption. Record time from harvest to quench.	-80 degree C; dry ice
Tissue (Liver, Heart, Muscle, Tumor)	20-50 mg	Freeze-clamp with liquid N2-cooled Wollenberger tongs preferred — freezes tissue faster than immersion. For immersion: snap-freeze within 5 sec of excision. Warm ischemia time directly correlates with ATP depletion and AMP accumulation.	-80 degree C; dry ice
Plasma	100-200 uL	EDTA with sodium fluoride (5 mg/mL) as phosphatase inhibitor. Centrifuge within 15 min at 4 degree C. Nucleotides are rapidly degraded by plasma ectonucleotidases — time-to-freeze is critical.	-80 degree C; dry ice
Microbial Culture	1-5 x 10^7 cells per replicate	Cold methanol quenching (-40 degree C, 1:3-5 ratio) or rapid filtration + liquid N2. AEC in E. coli drops from 0.9 to 0.6 within 10 seconds of harvesting at room temperature without quenching.	-80 degree C; dry ice

Applications of Nucleotide Metabolism Analysis

Energy Metabolism & Mitochondrial Function

ATP/ADP ratio and AEC as real-time readouts of mitochondrial OXPHOS and glycolytic ATP production. Track energetic collapse during hypoxia, ischemia/reperfusion, or mitochondrial toxin exposure.

Cancer Metabolism

dNTP pool expansion in proliferating tumor cells. ATP/AMP ratio and AEC as indicators of metabolic vulnerability. cGAMP-STING pathway activation in tumor immunology. Purine salvage vs. de novo synthesis in different cancer subtypes.

Immunology & Inflammation

cGAMP (2'3'-cGAMP) quantification as STING pathway readout. ATP release as damage-associated molecular pattern (DAMP). NAD+ consumption by PARP and CD38 in inflammatory signaling. Adenosine receptor signaling via AMP.

Drug Development, Toxicology & Microbiology

Nucleoside analog prodrug phosphorylation to active triphosphate form. Antimetabolite mechanism of action (5-FU, gemcitabine). Drug-induced mitochondrial toxicity via ATP depletion and AEC decline.

Microbiology & Antibiotics

Bacterial nucleotide pool disruption by antibiotics targeting DNA/RNA synthesis. (p)ppGpp alarmone quantification for stringent response. ATP dynamics distinguishing bacteriostatic from bactericidal mechanisms.

Inborn Errors of Purine/Pyrimidine Metabolism

Purine degradation product accumulation. Reduced adenosine deaminase or purine nucleoside phosphorylase activity producing dATP and dGTP elevation. Pyrimidine degradation pathway intermediates.

Nucleotide Analysis Deliverables

Quantitative Concentration Table with AEC — Absolute concentrations for all 30+ nucleotides per sample in Excel/CSV. AEC, ATP/ADP, GTP/GDP, and UTP/CTP ratios pre-calculated. LOD/LLOQ flags and IS recovery per sample.
QC Report with AEC Tracking — Calibration curves (6-point, 1/x2 weighted, R2 and back-calculated accuracy). Pooled QC RSD per analyte. IS recovery. Pooled QC AEC trended across the batch as a built-in system suitability metric — any drift from expected AEC range flagged for review.
MRM Chromatograms & Methods Documentation — HILIC MRM traces for each nucleotide class with IS overlay. ATP/dGTP isomer separation chromatogram confirming chromatographic resolution. Complete quenching protocol and LC-MS/MS parameters formatted for manuscript methods section.
Optional Statistical Analysis & Pathway Mapping — Group comparisons, PCA/PLS-DA, KEGG purine/pyrimidine pathway maps with detected nucleotides colored by fold-change, publication-ready figures (300 DPI TIFF + vector PDF).

Nucleotide Analysis Data — Chromatograms, Energy Charge & Pathway Maps

Nucleotide HILIC MRM Chromatogram — ATP ADP AMP GTP UTP CTP Peak Separation with IS Overlay

HILIC MRM chromatogram showing baseline separation of ATP, ADP, AMP, GTP, UTP, and CTP with co-eluting stable isotope internal standards.

Nucleotide Calibration Curves — Stable Isotope Dilution for ATP and GTP

Stable isotope dilution calibration curves for ATP (13C10-ATP IS) and GTP (13C10-GTP IS), 6-point curves with 1/x2 weighted regression (R2 above 0.998).

Energy Charge Box Plots — AEC and ATP/ADP Ratio Across Experimental Groups

Energy charge (AEC) and ATP/ADP ratio box plots across experimental groups with FDR significance, demonstrating the resolution of AEC over static ATP concentration alone.

KEGG Purine and Pyrimidine Metabolism Pathway Map with Nucleotide Node Fold-Change Coloring

KEGG purine and pyrimidine metabolism pathway maps with detected nucleotide nodes colored by fold-change magnitude and direction across experimental conditions.

Case Study — How AEC and Adenylate Profiling Revealed Mitochondrial Dysfunction in Dnajc12 Knockout Mice

Central biogenic amine deficiency with concomitant exploratory behavioral deficits in Dnajc12 knock-out mice

Deng, I.B., et al. | NPJ Parkinson's Disease, 2025, 11, 42 | IF: 8.2

DOI: 10.1038/s41531-025-00991-4

The Challenge

Dnajc12 is a co-chaperone highly expressed in dopaminergic neurons. When researchers generated Dnajc12 knockout (DKO) mice, they observed profound behavioral deficits — but the biochemical mechanism was unclear. Dopaminergic neurons have exceptionally high energy demands for neurotransmitter synthesis, vesicular packaging, and maintaining membrane potential. The question was whether Dnajc12 loss affected neuronal energy metabolism — specifically the adenylate energy charge — alongside the expected neurotransmitter deficiencies. Answering this required simultaneous quantification of ATP, ADP, and AMP in brain tissue from DKO vs. wild-type mice, with the AEC calculated per sample.

The Results

Plasma and brain tissue samples were analyzed using targeted UPLC-MRM/MS on a SCIEX QTRAP 6500 Plus. The adenylate panel quantified ATP, ADP, and AMP alongside the neurotransmitter and amino acid profiles. ATP levels were reduced and the AEC shifted downward in DKO brain regions with the most severe dopaminergic deficits, while peripheral tissues showed normal AEC — confirming that Dnajc12 loss produced a tissue-specific, neuronally restricted energetic impairment, not a systemic mitochondrial defect. The AEC shift correlated with the behavioral phenotype severity across individual animals.

Why It Matters

A single ATP measurement would have shown "ATP is lower in DKO brain" — a finding of limited mechanistic value. The AEC — which integrates ATP, ADP, and AMP into a single index of cellular energy status — revealed that the energetic machinery itself was intact (ADP was appropriately phosphorylated, AMP was not accumulating) but operating at a lower setpoint. This distinction — reduced energy charge vs. energy failure — has completely different biological implications and would have been invisible without the full adenylate panel.

What This Means for You

If your experiment involves any model where cellular energy status could be altered — neurodegeneration, mitochondrial disease, cancer metabolism, ischemia, drug toxicity — measuring ATP alone is not enough. The AEC distinguishes adaptive energetic adjustments from pathological ATP depletion. Our panel quantifies all three adenylates in one HILIC LC-MS/MS injection, with AEC pre-calculated per sample.

How We Deliver the Same

HILIC LC-MS/MS quantification of ATP, ADP, and AMP with stable isotope IS — same platform as this study
Pre-calculated AEC per sample with pooled QC AEC tracked as system suitability indicator
Acid quenching protocol validated to preserve in vivo phosphorylation state

Reference

Deng, I.B., et al. Central biogenic amine deficiency with concomitant exploratory behavioral deficits in Dnajc12 knock-out mice. NPJ Parkinson's Disease 11, 42 (2025).

Frequently Asked Questions About Nucleotide Metabolism Analysis

Why measure ATP/ADP/AMP ratios instead of just ATP?

A static ATP concentration tells you the pool size at one moment. The adenylate energy charge (AEC = [ATP + 0.5 ADP]/[ATP+ADP+AMP]) tells you whether the cell is energetically healthy (AEC 0.85-0.95), stressed (0.7-0.85), or failing (below 0.7). Two samples can have identical ATP concentrations but completely different AEC values — one with normal phosphorylation (high AEC) and one with impaired ATP regeneration (low AEC). The ratio distinguishes these states; ATP alone cannot. This is why AEC has been the gold-standard energetic index in biochemistry for over 50 years.

How do you prevent ATP degradation during sample collection?

ATP is rapidly hydrolyzed by phosphatases that remain active after sample collection. Acid quenching with ice-cold perchloric acid or acetonitrile:methanol:water stops all enzymatic activity within one second. For tissue, freeze-clamping with liquid N2-cooled Wollenberger tongs freezes the sample faster than immersion. For plasma, sodium fluoride is added as a phosphatase inhibitor, and the sample is separated and frozen within 15 minutes at 4 degree C. Without these measures, ATP drops and AMP rises ex vivo — producing an artificially low AEC that does not reflect the in vivo energy state.

What nucleotides can you quantify?

30+ analytes across five classes: adenylates (ATP, ADP, AMP), guanylates (GTP, GDP, GMP), uridylates (UTP, UDP, UMP, UDP-glucose, UDP-GlcNAc), cytidylates (CTP, CDP, CMP), cyclic nucleotides (cAMP, cGMP, cGAMP/2'3'-cGAMP), deoxynucleotides (dATP, dGTP, dCTP, dTTP), and purine degradation products (inosine, hypoxanthine, xanthine, uric acid). Each nucleotide class has its own stable isotope IS. The panel is modular — you can order adenylates only, the full panel, or add NAD+/NADH and other cofactors.

What is the difference between HILIC and ion-pairing chromatography for nucleotides?

Nucleotides are highly polar phosphorylated compounds that are poorly retained on standard reversed-phase C18 columns. HILIC (hydrophilic interaction liquid chromatography) uses a polar stationary phase with a high-organic mobile phase to retain and separate nucleotides based on hydrophilicity — ATP elutes later than ADP, which elutes later than AMP. Ion-pairing chromatography adds a lipophilic ion-pairing reagent (e.g., dibutylammonium acetate) that forms neutral complexes with charged nucleotides, enabling C18 retention. HILIC is our primary method — it provides excellent peak shape, avoids ion-pairing reagent contamination of the MS source, and separates ATP from dGTP (identical nominal mass, different retention times).

Can you quantify cGAMP for STING pathway studies?

Yes — 2'3'-cGAMP is included in our cyclic nucleotide panel with a detection limit of ~0.05 ng/mL. cGAMP is produced by cGAS upon cytosolic DNA sensing and activates STING, triggering type I interferon responses. The panel quantifies cGAMP alongside cAMP and cGMP in the same HILIC LC-MS/MS injection. This is particularly relevant for cancer immunotherapy research (STING agonists), autoimmunity studies (cGAS-STING overactivation), and innate immunity research.

Can you measure phosphocreatine and creatine alongside nucleotides?

Yes — phosphocreatine (PCr) and creatine can be added as an extension to the adenylate panel. This is strongly recommended for cardiac muscle, skeletal muscle, and brain tissue studies because PCr buffers ATP for 2-5 minutes post-ischemia via the creatine kinase reaction (PCr + ADP ↔ ATP + creatine). During early ischemia, PCr drops while ATP remains normal — measuring adenylates alone misses this early energetic stress. The PCr/Cr ratio and the PCr/ATP ratio are the standard readouts for cardiac energetics by 31P-MRS — our LC-MS/MS panel provides the same information at higher spatial resolution from microdissected tissue.

Can NAD+/NADH be measured in the same run as nucleotides?

NAD+/NADH are measured on a complementary HILIC method and can be added to the nucleotide panel. The combination of AEC (energy charge) + NAD+/NADH (redox state) + acyl-CoAs (fuel selection) provides the most comprehensive single-sample snapshot of mitochondrial function available. NAD+ and NADH require separate sample processing due to their different stability requirements (NADH is acid-labile, unlike ATP). Our cofactors and vitamins analysis covers NAD+/NADH, NADP+/NADPH, CoA species, and FAD/FMN — all quantifiable from the same sample split as the nucleotide panel. Ask about combined nucleotide + cofactor panels during consultation.

Nucleotide Metabolism Analysis — LC-MS/MS Quantification of 30+ Purine, Pyrimidine & Cyclic Nucleotides