ABSTRACT
Hyperpolarization-enhanced magnetic resonance imaging can be used to study biomolecular processes in the body, but typically requires nuclei such as 13 C, 15 N, or 129 Xe due to their long spin-polarization lifetimes and the absence of a proton-background signal from water and fat in the images. Here we present a novel type of 1 H imaging, in which hyperpolarized spin order is locked in a nonmagnetic long-lived correlated (singlet) state, and is only liberated for imaging by a specific biochemical reaction. In this work we produce hyperpolarized fumarate via chemical reaction of a precursor molecule with para-enriched hydrogen gas, and the proton singlet order in fumarate is released as antiphase NMR signals by enzymatic conversion to malate in D2 O. Using this model system we show two pulse sequences to rephase the NMR signals for imaging and suppress the background signals from water. The hyperpolarization-enhanced 1 H-imaging modality presented here can allow for hyperpolarized imaging without the need for low-abundance, low-sensitivity heteronuclei.
ABSTRACT
BACKGROUND: Reconstruction after pan-plexus root avulsions often includes gracilis free functioning muscle transfer. For elbow flexion reconstruction, the free functioning muscle transfer distal tendon is inserted into the biceps tendon or more distally (i.e., flexor digitorum profundus/flexor pollicis longus tendons) for combined elbow and finger flexion; the theoretical drawback of the latter approach is weaker elbow flexion. The authors compared elbow flexion strength with a biceps tendon versus a flexor digitorum profundus/flexor pollicis longus tendon attachment to determine which insertion point resulted in better elbow flexion. METHODS: Thirty-nine patients underwent free functioning muscle transfer with either a biceps tendon or a distal attachment. Groups were compared on postoperative elbow flexion strength, preoperative and postoperative Disabilities of the Arm, Shoulder, and Hand questionnaire scores, range of motion, and other surgical and demographic characteristics. A biomechanical analysis simulating different tendon attachments determined which reconstruction resulted in optimal elbow flexion mechanics. RESULTS: Distal tendon attachment was associated with M3 or M4 elbow flexion and greater range of motion compared with the biceps tendon attachment (p < 0.05). There were no statistically significant improvements in Disabilities of the Arm, Shoulder, and Hand questionnaire scores. Biomechanical analysis demonstrated that all distal tendon attachments studied generated a 15 to 30 percent greater torque compared with the biceps tendon attachment; this was true for attachments either at the flexor digitorum profundus/flexor pollicis longus tendon, or directly at the radius at 10 cm or 15 cm from the elbow axis of rotation. CONCLUSIONS: The flexor digitorum profundus/flexor pollicis longus tendon attachment of the gracilis free functioning muscle transfer distal tendon was superior in achieving elbow flexion strength. Patients with only elbow flexion reconstruction may also benefit from a flexor digitorum profundus/flexor pollicis longus tendon attachment or from a more distal attachment to the radius. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.
Subject(s)
Brachial Plexus/injuries , Free Tissue Flaps/transplantation , Gracilis Muscle/transplantation , Peripheral Nerve Injuries/surgery , Plastic Surgery Procedures/methods , Tendons/surgery , Adult , Biomechanical Phenomena , Elbow Joint/physiology , Female , Follow-Up Studies , Humans , Male , Middle Aged , Range of Motion, Articular , Retrospective Studies , Treatment OutcomeABSTRACT
Post-translational modification plays an important role in the biological functions of many proteins. Characterization of such modifications is crucial in the development of recombinant protein-based vaccines. Liquid Chromatography coupled with Mass Spectrometry (LC/MS) provides a powerful tool with high resolution and accuracy to characterize proteins and their post-translational modifications. The technique was applied to characterization of a Lyme vaccine protein rOspA (recombinant Outer surface protein A). The results demonstrate that LC/MS could be used to resolve and characterize various forms of post-translational lipidation of the protein. It was this detailed structural information that made it possible to validate a method for quantitative determination of the lipidation forms of rOspA.
