A new electrochemical method that mimics phosphorylation of the core tau peptide K18 enables kinetic and structural analysis of intermediates and assembly.

Tau protein's reversible assembly and binding of microtubules in brain neurons are regulated by charge-neutralizing phosphorylation, while its hyperphosphorylation drives the irreversible formation of cytotoxic filaments associated with neurodegenerative diseases. However, the structural changes that facilitate these diverse functions are unclear. Here, we analyzed K18, a core peptide of tau, using newly developed spectroelectrochemical instrumentation that enables electroreduction as a surrogate for charge neutralization by phosphorylation, with simultaneous, real-time quantitative analyses of the resulting conformational transitions and assembly. We observed a tipping point between behaviors that paralleled the transition between tau's physiologically required, reversible folding and assembly and the irreversibility of assemblies. The resulting rapidly electroassembled structures represent the first fibrillar tangles of K18 that have been formed in vitro at room temperature without using heparin or other charge-complementary anionic partners. These methods make it possible to (i) trigger and analyze in real time the early stages of conformational transitions and assembly without the need for preformed seeds, heterogenous coacervation, or crowding; (ii) kinetically resolve and potentially isolate never-before-seen early intermediates in these processes; and (iii) develop assays for additional factors and mechanisms that can direct the trajectory of assembly from physiologically benign and reversible to potentially pathological and irreversible structures. We anticipate wide applicability of these methods to other amyloidogenic systems and beyond.

Low Voltage Voltammetry Probes Proton Dissociation Equilibria of Amino Acids and Peptides.

Platinum-catalyzed electrochemical reduction of dissociable protons at low potentials was used to investigate proton dissociation equilibria of freely diffusing and peptide-incorporated charged amino acids. We first demonstrate with five charged essential amino acids and their analogs that the electrochemically induced deprotonation of each amino acid occurs at distinct formal reduction potential. Moreover, the observed direct reduction for all the charged species, excluding arginine, occurs at low potentials suitable for investigation under aqueous conditions (-0.4 to -0.9 V vs Ag/AgCl). The direct proton reduction was resolved via deconvolution of the observed differential pulse voltammogram (DPV) from background hydronium reduction and water electrolysis. A linear correlation was found between the formal reduction potentials and the pKa values of the dissociable protons hosted by various molecular moieties in the amino acids and their analogs and further verified with tripeptides. DPV of poly(l-lysine) decamer (Lys10) distinctively resolved the pKa values of the amino groups in the side chains and N-terminus, at a resolution not possible by conventional acid-base titration. This work demonstrates selective electrochemical titration of dissociable protons in charged amino acids in the free state and as residues in biomolecules, as well as the utility of DPV to indirectly interrogate local electrostatic environments that are essential to the stability and function of biomolecules.

Comparison of autologous blood, corticosteroid, and saline injection in the treatment of lateral epicondylitis: a prospective, randomized, controlled multicenter study.

PURPOSE: We compared saline, corticosteroid, and autologous blood injections for lateral epicondylitis in a prospective, blinded, randomized, controlled trial. The null hypothesis was that patient-rated outcomes after autologous blood injection would not be superior to corticosteroid and saline injections. METHODS: Patients with clinically diagnosed lateral epicondylitis of less than 6 months' duration were randomized into 1 of 3 groups to receive a 3-mL injection of saline and lidocaine, corticosteroid and lidocaine, or autologous blood and lidocaine. Of 34 subjects who enrolled, 28 completed follow-up. A total of 10 were randomized to the saline group, 9 to the autologous blood group, and 9 to the steroid group. Every participant had 3 mL blood drawn, and the injection syringe was foil-covered to prevent the subject from knowing the contents. The primary outcome measure was the Disabilities of the Arm, Shoulder, and Hand (DASH) score. Patients completed a pain visual analog scale, DASH, and the Patient-Rated Forearm Evaluation before injection and at 2 weeks, 2 months, and 6 months after injection. We performed statistical analysis using repeated measures of analyses of variance. RESULTS: There were no significant differences in DASH scores among the 3 groups at 2- and 6-month follow-up points, with the mean scores for saline at 20 and 10, respectively, compared with 28 and 20 for autologous blood and 28 and 13 for steroid injections. Secondary measures showed similar findings, with outcomes scores showing improvement in all 3 groups. CONCLUSIONS: In this prospective, randomized, controlled trial, autologous blood, corticosteroid, and saline injection provide no advantage over placebo saline injections in the treatment of lateral epicondylitis. Patients within each injection group demonstrated improved outcome scores over a 6-month period.

Gas-surface chemical reactions at high collision energies?

Most gas-surface chemical reactions occur via reaction of adsorbed species to form a thermal-energy ( approximately kT) product; however, some instances exist where an energetic projectile directly reacts with an adsorbate in a single-collision event to form a hyperthermal product (with a kinetic energy of a few eV). Here we show for the first time that 30-300 eV F(+) bombardment of fluorinated Ag and Si surfaces produces "ultrafast" F(2)(-) products with exit energies of up to 90 eV via a multistep direct-reaction mechanism. Experiments conclusively show that the projectile F atom ends up in the fast molecular product despite the fact that the impact energy is far greater than typical bond energies.

A comparison of the effectiveness of open and closed endotracheal suction.

OBJECTIVE: To compare the effectiveness of open and closed endotracheal suction in recovering thin and thick secretions in normal and injured lungs during conventional and high frequency ventilation. DESIGN AND SETTING: Randomised study in a paediatric intensive care model in the animal research laboratory of a tertiary paediatric hospital. SUBJECTS: 16 New Zealand White rabbits. INTERVENTIONS: Anaesthetised animals were intubated with a 3.5-mm endotracheal tube. Simulated thin and thick secretions (iopamidol 2 ml, a watery radio-opaque fluid, and fluorescent mucin 1 ml) were instilled in turn 1 cm below the tube tip through a catheter placed via a tracheostomy. Open or closed suction, randomly assigned, was applied for 6s at -140 mmHg using a 6-F gauge catheter. Following lung injury with repeated saline lavage the procedure was repeated on conventional and high frequency ventilation. MEASUREMENTS AND RESULTS: Iopamidol recovery was determined by digitally subtracting the post-contrast and post-suction radiographic images. Mucin recovery was determined by fluorescence assay of the aspirate. In the normal lung similar amounts were recovered by both suction methods. In the lavaged lung closed suction recovered less iopamidol during conventional (22 +/- 7.5%) and high frequency ventilation (11 +/- 2.4%) than open suction (36 +/- 2% and 22 +/- 8.1%, respectively). Mucin recovery was less with closed suction during conventional 32 +/- 28 microl) and high frequency ventilation (30 +/- 31 microl) than with open suction (382 +/- 235 microl and 24 +/- 153 microl). CONCLUSIONS: In the injured lung closed suction was less effective than open suction at recovering thin and thick simulated secretions, irrespective of ventilation mode.

Comminuted olecranon fractures: a comparison of plating methods.

The relative strength of posterior plating and dual medial-lateral plating for comminuted olecranon fractures has not been evaluated. Fifteen male cadaveric elbows with simulated highly comminuted olecranon fractures were tested to failure via cantilever bending. The strength of dual medial-lateral plates and a single posterior plate with and without an intramedullary screw was evaluated. The mean bending moment at failure for the dual-plated specimens was 30.0 +/- 7.5 Nm. The mean bending moment at failure for specimens with a posterior plate without an intramedullary screw was 34.5 +/- 9.1 Nm. The mean bending moment at failure for specimens with a posterior plate and an intramedullary screw was 44.5 +/- 6.9 Nm; this was significantly greater than for dual-plated specimens (P < .05) but not for specimens with a posterior plate without an intramedullary screw. The posterior plate with an intramedullary screw was the most stable construct tested and may, therefore, be the preferred method of fixation for comminuted olecranon fractures. This construct was significantly (48%) stronger than dual medial and lateral plating.

Recurrent neuroma formation after lateral arm free flap coverage with neurorraphy to the posteroantebrachial nerve.

We report a patient with previous wrist trauma and development of a symptomatic neuroma of the palmar cutaneous branch of the median nerve. The patient had previously been successfully treated with lateral arm free flap coverage with neurorrhaphy to a segment of the posteroantebrachial cutaneous nerve carried with the flap. Two years following this procedure the patient experienced re-onset of symptoms prompting surgical exploration of the area. At the time of operation a recurrent neuroma was found at the free distal terminus of the transferred posteroantebrachial cutaneous nerve. The neuroma was repositioned into the distal radius via a burr hole with relief of symptoms.