Chemical Shift Differences Research Articles

Charge order and structure transformation of hydrated cesium cobaltates revealed by variable‐temperature 133Cs NMR spectroscopy

AbstractVariable temperature 133Cs‐NMR experiments were performed to probe the local environment of the cesium ions in hydrated cesium cobaltates (Cs0.2CoO2·0.63H2O) from 170 to 390 K. Temperature dependence of the chemical shifts and linewidths reveals two‐phase transitions at a temperature near 200 and 350 K. Three inequivalent cesium sites are observed as the temperature is reduced below 200 K, indicating restricted motion of the cesium ions and a tendency to electron localization on cobalt ions. The results provide evidence for a definite order of the cesium ions and the charge order of the cobalt ions in the CoO2 layers. Two inequivalent cesium sites with larger chemical shift differences are observed as the temperature is above 350 K, indicating a spectacular change in the space between the CoO2 planes, which provides evidence for the transition between the bilayer‐hydrated and monolayer‐hydrated structures.

Piperhancosides A−C, new lignan glycosides from the stems of Piper hancei Maxim

Three new lignan glycosides, piperhancosides A−C (1−3), and two known compounds (4−5) were isolated from the n-BuOH extract of the stems of Piper hancei Maxim. The planar structures of the new compounds were elucidated by extensive spectroscopic analyses. Their relative and absolute configurations were determined by coupling constants, chemical shift differences, acid hydrolysis, enzymatic hydrolysis, and experimental ECD spectra. All the isolates were evaluated for their antineuroinflammatory and antioxidant activities, and compounds 4 and 5 showed significant DPPH.+ radical scavenging ability with EC50 value of 14.07 and 16.48 μM, respectively.

Resting-State Brain Temperature: Dynamic Fluctuations in Brain Temperature and the Brain-Body Temperature Gradient.

While fluctuations in healthy brain temperature have been investigated over time periods of weeks to months, dynamics over shorter time periods are less clear. To identify physiological fluctuations in brain temperature in healthy volunteers over time scales of approximately 1 hour. Prospective. A total of 30 healthy volunteers (15 female; 26 ± 4 years old). 3 T; T1-weighted magnetization-prepared rapid gradient-echo (MPRAGE) and semi-localized by adiabatic selective refocusing (sLASER) single-voxel spectroscopy. Brain temperature was calculated from the chemical shift difference between N-acetylaspartate and water. To evaluate within-scan repeatability of brain temperature and the brain-body temperature difference, 128 spectral transients were divided into two sets of 64-spectra. Between-scan repeatability was evaluated using two time periods, ~1-1.5 hours apart. A hierarchical linear mixed model was used to calculate within-scan and between-scan correlations (Rw and Rb , respectively). Significance was determined at P ≤ .05. Values are reported as the mean ± standard deviation. A significant difference in brain temperature was observed between scans (-0.4°C) but body temperature was stable (P=.59). Brain temperature (37.9 ± 0.7°C) was higher than body temperature (36.5 ± 0.5°C) for all but one subject. Within-scan correlation was high for brain temperature (Rw =0.95) and brain-body temperature differences (Rw =0.96). Between scans, variability was high for both brain temperature (Rb =0.30) and brain-body temperature differences (Rb =0.41). Significant changes in brain temperature over time scales of ~1 hour were observed. High short-term repeatability suggests temperature changes appear to be due to physiology rather than measurement error. 2 TECHNICAL EFFICACY: Stage 1.

Selective Homodecoupled 1D-1H NMR Experiment for Unravelling Enantiomers.

1H NMR spectroscopy is a quick and easy tool to resolve enantiomers. However, the paradigm of resolution of enantiomers by 1H NMR is a difficult task due to the minor chemical shift differences and overlap of the resonances of the enantiomers. In the current study, we have performed the conventional selective homodecoupling 1D-1H NMR experiment to achieve chiral resolutions. The predominant features of the proposed methods are (a) high sensitivity as opposed to routinely employed pure shift NMR experiments, (b) easy optimization like conventional 1D-1H NMR, and (c) an artifact-free spectrum. The application of the method has been exhibited in the measurement of proton chemical shift differences between diastereomers and enantiomer excess (ee). The broad use of the proposed method was demonstrated by employing the six samples utilizing the chiral solvating and derivatizing agents.

Exploring the use of cobalt(II) dipolar shifts in refining the structure of a zinc finger peptide

The uses of dipolar shifts due to cobalt(II) substituted for zinc(II) in a consensus zinc finger peptide for refining the NMR-determined structure were examined. Substantial differences between the calculated and observed chemical shift differences between the cobalt(II) and zinc(II) complexes were observed when these dipolar shifts were not used as constraints in the structure refinement. However, inclusion of these constraints resulted in excellent agreement with minor adjustments in the structure and a slight improvement in the precision of the structure determination. Other calculations revealed that the dipolar shifts were not adequate to determine the overall folded structure by themselves, but were useful in increasing the accuracy and precision of a structure determined based only on nuclear Overhauser effects constraints involving only backbone atoms.

Active conductive head cooling of normal and infarcted brain: A magnetic resonance spectroscopy imaging study

Active conductive head cooling is a simple and non-invasive intervention that may slow infarct growth in ischemic stroke. We investigated the effect of active conductive head cooling on brain temperature using whole brain echo-planar spectroscopic imaging. A cooling cap (WElkins Temperature Regulation System, 2nd Gen) was used to administer cooling for 80 minutes to healthy volunteers and chronic stroke patients. Whole brain echo-planar spectroscopic imaging scans were obtained before and after cooling. Brain temperature was estimated using the Metabolite Imaging and Data Analysis System software package, which allows voxel-level temperature calculations using the chemical shift difference between metabolite (N-acetylaspartate, creatine, choline) and water resonances. Eleven participants (six healthy volunteers, five post-stroke) underwent 80 ± 5 minutes of cooling. The average temperature of the coolant was 1.3 ± 0.5°C below zero. Significant reductions in brain temperature (ΔT = –0.9 ± 0.7°C, P = 0.002), and to a lesser extent, rectal temperature (ΔT = –0.3 ± 0.1°C, P = 0.03) were observed. Exploratory analysis showed that the occipital lobes had the greatest reduction in temperature (ΔT = –1.5 ± 1.2°C, P = 0.002). Regions of infarction had similar temperature reductions to the contralateral normal brain. Future research could investigate the feasibility of head cooling as a potential neuroprotective strategy in patients being considered for acute stroke therapies.

NMR spectroscopy, excited states and relevance to problems in cell biology - transient pre-nucleation tetramerization of huntingtin and insights into Huntington's disease.

Solution nuclear magnetic resonance (NMR) spectroscopy is a powerful technique for analyzing three-dimensional structure and dynamics of macromolecules at atomic resolution. Recent advances have exploited the unique properties of NMR in exchanging systems to detect, characterize and visualize excited sparsely populated states of biological macromolecules and their complexes, which are only transient. These states are invisible to conventional biophysical techniques, and play a key role in many processes, including molecular recognition, protein folding, enzyme catalysis, assembly and fibril formation. All the NMR techniques make use of exchange between sparsely populated NMR-invisible and highly populated NMR-visible states to transfer a magnetization property from the invisible state to the visible one where it can be easily detected and quantified. There are three classes of NMR experiments that rely on differences in distance, chemical shift or transverse relaxation (molecular mass) between the NMR-visible and -invisible species. Here, I illustrate the application of these methods to unravel the complex mechanism of sub-millisecond pre-nucleation oligomerization of the N-terminal region of huntingtin, encoded by exon-1 of the huntingtin gene, where CAG expansion leads to Huntington's disease, a fatal autosomal-dominant neurodegenerative condition. I also discuss how inhibition of tetramerization blocks the much slower (by many orders of magnitude) process of fibril formation.

Simultaneous Discrimination and Quantification of Enantiomeric Amino Acids under Physiological Conditions by Chiral 19F NMR Tag.

Enantiomeric analysis is of great significance in chemistry, chemical biology and pharmaceutical research. We herein propose a chiral 19F NMR tag containing an amino reactive NHS group to discriminate the enantiomeric amino acids under physiological conditions by NMR spectroscopy. The chiral 19F NMR tag readily forms stable amide products with the amino acids in aqueous solution. The stereospecific chemistry of enantiomeric amino acids is discriminated by a stereogenic carbon bonded with a 19F atom and is therefore decoded by the 19F reporter and manifested in the distinct 19F chemical shift. The chemical shift difference (ΔΔδ) of the chiral 19F NMR tag derived enantiomeric amino acids variants has a broad chemical shift range between -1.13 to 1.68 ppm, indicating the high sensitivity of the chiral 19F NMR tag to the stereospecific environment surrounding the individual amino acids. The distinguishable chemical shift produced by the chiral 19F NMR tag permits simultaneous discrimination and quantification of the enantiomeric amino acids in a mixture. The high fidelity of the chiral 19F NMR tag affords high-accuracy determination of the enantiomeric composition of amino acids by simple 1D NMR under physiological conditions.

Homonuclear J-coupling spectroscopy using J-synchronized echo detection

In the strong coupling regime with J-coupling much larger than chemical shift differences, J-coupling spectroscopy enables spectral identification of molecules even when conventional NMR fails. While this classically required the presence of a heteronucleus, we recently showed that J-coupling spectra can be acquired in many homonuclear systems using spin-lock induced crossing (SLIC). Here, we present an alternative method using a spin echo train in lieu of a spin-locking SLIC pulse, which has a number of advantages. In particular, spin echo acquisition within the pulse train enables simultaneous collection of time and frequency data. The resulting 2D spectrum can be used to study dynamic spin evolution, and the time domain data can be averaged to create a 1D J-coupling spectrum with increased signal-to-noise ratio.

Methods for Determination of Absolute Configurations of Chiral Diols by THENA Ester and NMR Shift Difference

AbstractDetermination of the absolute configuration of chiral secondary diols by chiral derivatizing agent (CDA) and NMR shift difference is of great challenge due to the complication from the interference of the aromatic anisotropic shielding effect of the two CDAs in close proximity. In this work, tetrahydro-1,4-epoxynaphthalene-1-carboxylic acid (THENA) was introduced as an alternative CDA for diols to overcome such complexity. Since the deshielding effect of THENA is weaker than the shielding effect of other CDAs, THENA would allow the direct analysis of the chemical shift difference in determining the absolute configuration of the chiral diols. In addition, an analytical method based on Riguera’s model could also be used to confirm the assignment. With a good agreement between the assigned configuration based on both analytical models, the absolute configuration of the chiral diols could be assigned with reliability.

19F magnetic resonance probes for detecting formaldehyde

Herein we report two separate 19F magnetic resonance (MR) probes responsive towards formaldehyde. Both agents were synthesized in a single step via aminoallylation of either 4-fluorobenzaldehyde (1FA) or 4-(trifluoromethyl)benzaldehyde (3FA) with ammonia and allylboronic acid pinacol ester. Condensation of the resulting homoallylic amines 1FA and 3FA with formaldehyde, followed by a 2-aza-Cope rearrangement and subsequent hydrolysis affords 4-fluorobenzaldehyde and 4-(trifluoromethyl)benzaldehyde, respectively. In the case of 1FA, this transformation is evidenced by a concomitant downfield shift in the 19F MR signal from −115 ppm to −103 ppm. Further, this transformation is selective towards formaldehyde over other reactive carbonyl species. While 3FA exhibits similar selectivity towards formaldehyde, this more sensitive probe is limited by the small chemical shift difference (0.7 ppm) following its activation.

31 P MRSI at 7 T enables high-resolution volumetric mapping of the intracellular magnesium ion content in human lower leg muscles.

The non-invasive determination of the free magnesium ion concentration ([Mg2+free ]) using 31 P MRSI in vivo is of interest in research on various pathologies, e.g. diabetes. The purpose of this study was to demonstrate the potential of 31 P MRSI at 7 T to enable volumetric, high-resolution mapping of [Mg2+free ]. 3D 31 P MRSI datasets from the lower leg of three healthy volunteers were acquired at B0 = 7 T with a nominal spatial resolution of (8× 8× 16)mm3 in 56 min. Volumetric [Mg2+free ] maps were calculated based on the quantified local chemical shift difference between the α- and β-resonance of adenosine triphosphate (ATP) considering also local pH values. Mean [Mg2+free ] values from three different muscle groups were compared. To demonstrate the potential of reducing the measurement time, the analysis was repeated on the acquired MRSI data retrospectively reconstructed with fewer averages. The generated [Mg2+free ] maps revealed local differences, and mean [Mg2+free ] values of (1.08 ± 0.03)mM were found in the tibialis anterior, (0.91 ± 0.04)mM in the soleus and (0.98 ± 0.03)mM in the gastrocnemius medialis. The time-reduced 28-min scan resulted in comparable [Mg2+free ] maps, and mean values being in agreement with the values from the 56-min scan. 31 P MRSI at 7 T enables volumetric, high-resolution mapping of free magnesium ion content in human lower leg muscles. The measurement time of the 31 P MRSI acquisition can be reduced to 28 min, opening the potential to apply volumetric [Mg2+free ] mapping for the investigation of pathologies with altered magnesium homeostasis.

Isotopic Substitution Reveals the Importance of Aluminate Diffusion Dynamics in Gibbsite (Al(OH)3) Crystallization from Alkaline Aqueous Solution

Understanding molecular-scale factors governing the precipitation of aluminum hydroxides, such as gibbsite, under alkaline conditions is important for the formation of laterite deposits, as well as aluminum processing. However, mechanisms enabling tetrahedral aluminate ions to assemble into octahedral sites of the gibbsite lattice remain unclear. Formation of oligomeric complexes has been hypothesized as a critical intermediate step. Here, we report a study of gibbsite solubility in highly alkaline solutions using deuterium substitution to probe equilibrium and kinetic factors that could affect oligomeric intermediate formation, including the reactivity and the diffusivity of aluminate ions. When substituting sodium hydroxide with sodium deuteroxide, solution analysis shows a nearly 40% and 50% increase in gibbsite solubility in 2.4 and 3.3 mol·kg–1 total sodium solutions, respectively. Raman spectroscopy indicated that monomeric aluminate ions are the predominant species in solution irrespective of deuteration. However, both 27Al and 23Na nuclear magnetic resonance (NMR) spectroscopy revealed significant differences in chemical shifts in deuterated solutions, and analysis of 1H, 23Na, and 27Al diffusion coefficients with pulsed-field gradient, stimulated echo NMR spectroscopy shows a decrease in ion diffusivity with increasing total deuterium in solution, consistent with the notion of increasing strength in the hydrogen/deuterium bonding network. Because the relative change in 1H diffusion coefficients are commensurate with the difference in apparent solubility constants, there is evidence for an oligomeric intermediate whose steady-state concentration is maintained by the collision frequency of aluminate ions.

Bound nucleotide can control the dynamic architecture of monomeric actin

Polymerization of actin into cytoskeletal filaments is coupled to its bound adenine nucleotides. The mechanism by which nucleotide modulates actin functions has not been evident from analyses of ATP- and ADP-bound crystal structures of the actin monomer. We report that NMR chemical shift differences between the two forms are globally distributed. Furthermore, microsecond–millisecond motions are spread throughout the molecule in the ATP form, but largely confined to subdomains 1 and 2, and the nucleotide binding site in the ADP form. Through these motions, the ATP- and ADP-bound forms sample different high-energy conformations. A deafness-causing, fast-nucleating actin mutant populates the high-energy conformer of ATP-actin more than the wild-type protein, suggesting that this conformer may be on the pathway to nucleation. Together, the data suggest a model in which differential sampling of a nucleation-compatible form of the actin monomer may contribute to control of actin filament dynamics by nucleotide.

13C NMR investigations and order parameters of rod-like molecules with terminal phenyl and thiophene rings in mesogenic core✰

Rod-like mesogens with the rigid core constituted by a combination of phenyl and thiophene moieties reveal interesting orientational ordering behavior. In this article, four rod-like mesogens constructed with a terminal alkoxy chain on only one side of the mesogenic core with the other end terminated with either a phenyl or thiophene ring have been investigated using 13C NMR spectroscopy. The mesogen with the terphenyl moiety in the core exhibited polymesomorphism with nematic, smectic C, and smectic I mesophases with very high clearing temperatures. The replacement of terphenyl with terthiophene moiety resulted in suppression of polymesomorphism, with only nematic mesophase being observed. Mesogens with single terminal thiophene connected to two phenyl rings in the core also showed only the nematic mesophase for both the possibilities of linking the core to the thiophene ring at the 2- and 3- positions. One- and two- dimensional 13C NMR spectra have been obtained in the mesophases from which the alignment induced chemical shifts of the ring carbons and 13C-1H dipolar couplings, as well as the local order parameters, have been obtained. The considerable difference in 13C chemical shifts and the 13C-1H dipolar couplings of thiophene ring with change in position of the linking unit is attributed to the difference in the order parameters of the thiophene moiety between the two cases. The data obtained on the ordering of phenyl and thiophene rings in the core units offered information into the effect of replacing the phenyl ring with the thiophene ring. So also, the change of position of the link to the thiophene moiety provided important insights into the orientational behavior in the liquid crystalline phase and on the molecular structure.

NMR assignment of non-modified tRNAIle from Escherichia coli

tRNAs are L-shaped RNA molecules of ~ 80 nucleotides that are responsible for decoding the mRNA and for the incorporation of the correct amino acid into the growing peptidyl-chain at the ribosome. They occur in all kingdoms of life and both their functions, and their structure are highly conserved. The L-shaped tertiary structure is based on a cloverleaf-like secondary structure that consists of four base paired stems connected by three to four loops. The anticodon base triplet, which is complementary to the sequence of the mRNA, resides in the anticodon loop whereas the amino acid is attached to the sequence CCA at the 3′-terminus of the molecule. tRNAs exhibit very stable secondary and tertiary structures and contain up to 10% modified nucleotides. However, their structure and function can also be maintained in the absence of nucleotide modifications. Here, we present the assignments of nucleobase resonances of the non-modified 77 nt tRNAIle from the gram-negative bacterium Escherichia coli. We obtained assignments for all imino resonances visible in the spectra of the tRNA as well as for additional exchangeable and non-exchangeable protons and for heteronuclei of the nucleobases. Based on these assignments we could determine the chemical shift differences between modified and non-modified tRNAIle as a first step towards the analysis of the effect of nucleotide modifications on tRNA’s structure and dynamics.

Pulse induced resonance with angular dependent total enhancement of multi-dimensional solid-state NMR correlation spectra

We demonstrate a new resonance condition that obeys the relation Δδ=nνR/2, where Δδ is the chemical shift difference between two homonuclear-coupled spins, νR is the magic-angle spinning speed and n is an integer. This modulation on the rotational resonance recoupling condition is obtained by the application of rotor-synchronous 1H pulses when at least one proton is dipolar-coupled to one of the homonuclear spins. We suggest a new experimental scheme entitled ‘pulse induced resonance with angular dependent total enhancement’ (PIRATE) that can enhance proton-driven spin diffusion by the application of a single 1H pulse every rotor period. Experimental evidence is demonstrated on the two carbon spins of glycine and on the Y21M mutant of fd bacteriophage virus. Numerical simulations reveal the existence of the resonances and report on the important interactions governing these phenomena.

Acetylene Derivatives of Cationic Diazaoxatriangulenes and Diaza [4]Helicenes ‐ Access to Red Emitters and Planar Chiral Stereochemical Traits

Cationic triangulenes, and related helicenes, constitute a rich class of dyes and fluorophores, usually absorbing and emitting light at low energy, in the orange to red domains. Recently, to broaden the scope of applications, regioselective late‐stage functionalizations on these core moieties have been developed. For instance, with the introduction of electron‐donating groups (EDGs), important bathochromic shifts are observed pushing absorptions towards or in the near‐infrared (NIR) spectral domain while emissive properties disappear essentially completely. Herein, to upset this drawback, acetylene derivatives of cationic diazaoxa triangulenes (DAOTA) and [4]helicenes are prepared (16 examples). Contrary to other EDG‐functionalized derivatives, C≡C− functionalized products remain broadly fluorescent, with red‐shifted absorptions (Δλ abs up to 25 nm) and emissions (Δλ em up to 73 nm, Φ PL up to 51 %). Quite interestingly, a general dynamic stereoisomerism phenomenon is evidenced for the compounds derived from achiral DAOTA cores. At low temperature in 1H NMR spectroscopy (218 K), N−CH2 protons become diastereotopic with chemical shifts differences (Δδ) as high as +1.64 ppm. The signal coalescence occurs around 273 K with a barrier of ∼12 kcal mol−1. This phenomenon is due to planar chiral conformations (S p and R p configurations), induced by the geometry of the alkyl (n‐propyl) side‐chains next to the acetylenic substituents. Ion pairing studies with Δ‐TRISPHAT anion not only confirm the occurrence of the chiral conformations but evidence a moderate but definite asymmetric induction from the chiral anion onto the cations. Finally, DFT calculations offer a valuable insight on the geometries, the corresponding stereodynamics and also on the very large difference in NMR for some of the diastereotopic protons.

Abstract TP236: Brain And Infarct Temperature Changes With Active Conductive Head Cooling: A Magnetic Resonance Spectroscopy Imaging Study

Background and Purpose: Active conductive head cooling (HC) is a simple and non-invasive intervention that may potentially slow infarct growth in patients with stroke. Using magnetic resonance spectroscopy imaging (MRSI), we investigated the effect of HC on brain and systemic temperatures. Methods: A cooling cap (WElkins Temperature Regulation System, 2nd Gen) was used to administer HC for 80 minutes to healthy volunteers and patients at least 6 months following a large vessel occlusion stroke. Serial MRSI scans were obtained before and during HC. Brain temperature was estimated using the Metabolite Imaging and Data Analysis System software package, which allows voxel-level temperature calculations using the chemical shift difference between metabolite (N-acetylaspartate, creatine, choline) and water resonances. Rectal temperature, the 11-point Numerical Pain Rating Scale score, heart rate, and blood pressure were measured. The primary outcome was the mean difference in brain temperature before and after HC. Results: Eleven participants (6 healthy volunteers, and 5 post-stroke) had a total of 66 MRSI scans performed over 80±5 minutes of HC. An average absolute temperature of -1.3±0.5°C was delivered via the cooling cap to the scalp of the participants. Following HC, significant reductions in brain temperature (ΔT = -0.9±0.7°C, P =0.002), and to a lesser extent, rectal temperature (ΔT = -0.3±0.1°C, P =0.03) were observed. Linear regression analysis of all 66 MRSI scans showed a brain temperature-by-time gradient of -0.53°C per hour ( P =0.001). In the stroke patients, the temperature-by-time gradient within the infarct was -0.60°C per hour ( P =0.01). HC was well-tolerated, heart rate and blood pressure remained stable, the median (IQR) Numerical Pain Rating Scale score was 2.5 (1-3) at 80 minutes, and none developed shivering. Conclusions: HC was well-tolerated and resulted in potentially clinically meaningful reductions in brain and infarct temperature, with only slight reduction in systemic temperature. Future research should investigate the feasibility of HC as a potential neuroprotective strategy in patients being considered for acute stroke therapies such as mechanical thrombectomy.

P062 31P MRS and MRI phenotyping of muscle metabolic quality in IBD fatigue

Abstract Background Fatigue perception and exercise intolerance are common in inflammatory bowel disease (IBD). The mechanisms are unknown, although physical deconditioning is greater in fatigued relative to non-fatigued patients, suggesting an aetiological role for deconditioning. To assess peripheral muscle quality in Crohn’s disease (CD), we quantified the time-course of muscle phosphocreatine (PCr) recovery, which is wholly mitochondrial dependent, following ischaemic high-intensity exercise in fatigued CD and HV. Methods Participant body mass and regional body composition was assessed by DEXA. All MR data was collected using a 3T Philips Achieva scanner and a 14cm 31P coil on the medial gastrocnemius muscle. 1H mDIXON scans were acquired to image the calf prior to ischaemic plantar flexion exercise at 50% maximum voluntary contraction (MVC) using an MR-compatible ergometer (Trispect, Ergospect) during non-localized pulse-acquire 31P-MRS. 31P spectra were analysed using jMRUI Beta 6.0 using the AMARES function with prior knowledge. Cytosolic pH was estimated using the chemical shift difference between Pi and PCr peaks. Post exercise PCr recovery was quantified after reinstating limb blood flow. PCr recovery was expressed relative to baseline (non-ischaemic) signal amplitude and fit to a mono-exponential function in GraphPad prism. (PCr(t) = PCrinitial+(PCrend – PCrinitial)(1-exp(-k.t)) where t is the time from the start of non-ischaemic recovery, PCrinitial and PCrend is the PCr signal at the initial and end of recovery phases. An FSL and Matlab pipeline was used to obtain calf muscle volume and fat fraction from 1H mDIXON images. Results 13 quiescent CD patients (7 female, HBI 1±2, CRP <5) and 9 HVs (4 female) were matched for age (P = 0.986) and BMI (P = 0.845). General fatigue score was greater in CD (13 ± 4) relative to HV (8 ± 3) (t19=3.08, P = 0.006) (Table 1.) End-exercise muscle PCr depletion (%) (85.25 ± 10.12 vs 83.28 ± 7.8%, P = 0.639) and estimated end-exercise muscle pH (6.6 ± 0.2 vs 6.5 ± 0.2, P = 0.320) was consistent between HV and CD. The mean rate constant of PCr resynthesis (kPCr min-1) in CD (0.76 ± 0.23) was significantly less (t20 = 2.6, P = 0.016) than HV (1.03 ± 0.23). PCr recovery curves were well described using a mono-exponential function in CD (R2=0.98 ± 0.01, R2value) and HV (R2=0.96 ± 0.03) (Table 3). Conclusion The PCr resynthesis rate following intensity matched ischemic exercise was less in fatigued CD patients relative to HV. This points to peripheral muscle deconditioning and associated loss of mitochondrial mass as a driver of exercise intolerance in IBD. This may be amenable to exercise training intervention.