Overcoming Protein Orientation Mismatch Enables Efficient Nanoscale Light-Driven ATP Production

Adenosine triphosphate (ATP)-producing modules energized by light-driven proton pumps are powerful tools for the bottom-up assembly of artificial cell-like systems. However, the maximum efficiency of such modules is prohibited by the random orientation of the proton pumps during the reconstitution process into lipid-surrounded nanocontainers. Here, we overcome this limitation using a versatile approach to uniformly orient the light-driven proton pump proteorhodopsin (pR) in liposomes. pR is post-translationally either covalently or noncovalently coupled to a membrane-impermeable protein domain guiding orientation during insertion into preformed liposomes. In the second scenario, we developed a novel bifunctional linker, trisNTA-SpyTag, that allows for the reversible connection of any SpyCatcher-containing protein and a HisTag-carrying protein. The desired protein orientations are verified by monitoring vectorial proton pumping and membrane potential generation. In conjunction with ATP synthase, highly efficient ATP production is energized by the inwardly pumping population. In comparison to other light-driven ATP-producing modules, the uniform orientation allows for maximal rates at economical protein concentrations. The presented technology is highly customizable and not limited to light-driven proton pumps but applicable to many membrane proteins and offers a general approach to overcome orientation mismatch during membrane reconstitution, requiring little to no genetic modification of the protein of interest.

Rapid Estimation of Membrane Protein Orientation in Liposomes

The topological organization of proteins embedded in biological membranes is crucial for the tight interplay between these enzymes and their accessibility to substrates in order to fulfil enzymatic activity. The orientation of a membrane protein reconstituted in artificial membranes depends on many parameters and is hardly predictable. Here, we present a convenient approach to assess this important property independent of the enzymatic activity of the reconstituted protein. Based on cysteine‐specific chemical modification of a target membrane protein with a cyanine fluorophore and a corresponding membrane‐impermeable fluorescence quencher, the novel strategy allows rapid evaluation of the distribution of the two orientations after reconstitution. The assay has been tested for the respiratory complexes bo₃ oxidase and ATP synthase of Escherichia coli and the results agree well with other orientation determination approaches. Given the simple procedure, the proposed method is a powerful tool for optimization of reconstitution conditions or quantitative orientation information prior to functional measurements.

[Qualitative comparison of modified neurolept-, balanced and intravenous anesthesia. 2. Results of a clinical study, 1992]

The safety and tolerance of neuroleptanaesthesia (NLA), balanced anaesthesia (BAL), and intravenous anaesthesia with propofol (IVA) were analysed for the first time in a prospective, randomised clinical trial. METHODS. In all, 1318 surgical patients received either NLA, BAL, or IVA. Patients who had regional anaesthesia, were aged under 18 years, or were non-cooperative or vitally threatened (ASA class i.v. to V) did not participate in the study. Premedication and anaesthetic course were set up at a standard of 30% oxygen and 70% nitrous oxide. Incidents, events, and complications due to anaesthesia were obtained (IEC key of the German Society of Anaesthesia and Critical Care Medicine, DGAI). Furthermore, postanaesthetic alertness based on specific recovery tests and the quality of anaesthesia from the patient's viewpoint, rated by patient questionnaires from the DGAI were evaluated. All parameters were calculated and checked for statistical significance using the chi-square test. RESULTS AND DISCUSSION. The groups were broadly comparable with respect to age (P = 0.91), ASA class (P = 0.42), preoperative blood pressure (P = 0.36), and length of anaesthesia (P = 0.82). The anaesthesia, which averaged 103 min, comprised the following regimens: (1) NLA: 7.1 mg droperidol and 0.008 mg/kg body weight fentanyl, (2) IVA: 493.4 mg propofol and 0.004 mg/kg body weight fentanyl, and (3) BAL: 2.6 mg droperidol and 0.004 mg/kg body weight fentanyl with 0.4 vol.% isoflurane. With respect to anaesthetic risk, the following reactions were observed: the use of NLA led to a high incidence of tachycardia (P = 0.001), arrhythmias (P = 0.05), and hypertensive reactions (P = 0.001), whereas in the IVA group only hypotension (P = 0.0001) occurred. However, after the use of BAL none of the aforementioned complications were detectable to any considerable degree. Similarly, patients who had cardiac disease showed greater IEC changes after the use of NLA than after BAL or IVA (P = 0.02) (Tables 1 and 2). The heart rates and blood pressures during BAL and IVA were extremely stable, and therefore, vasoactive therapy was required considerably less in comparison to NLA (P = 0.001) (Table 4). Recovery after the use of IVA was strikingly rapid: the patient's responsiveness, orientation, and ability to concentrate was significantly better than after the other anaesthetic regimen (P = 0.01) (Table 5). With regard to the typical discomforts after anaesthesia, IVA was highly superior to BAL and NLA: nausea (P = 0.0003) and retching (P = 0.03) hardly ever occurred (Table 6). Due to the tolerable manner of waking up and rapid return of orientation and the ability to concentrate, IVA was highly favoured by the patients (P = < 0.01) (Table 7). CONCLUSION. The present results show clear clinical advantages of BAL and IVA in contrast to neuroleptanaesthesia. Due to the very low incidence of side effects such as nausea and vomiting IVA was highly recommended by the patients, at least in part because of the rapid recovery time.

[Quality comparison of modified neurolept-, balanced and intravenous anesthesia. 1. Study design and patient analysis of the Krefelder study 1992]

The choice of appropriate anaesthesia in a more or less seriously ill patient requires detailed information on the risk and tolerance of each specific anaesthetic regimen. The objective of this prospective, randomised clinical trial was to test the hypothesis that three regimens of general anaesthesia--neurolept-(NLA), balanced (BAL), and intravenous propofol anaesthesia (IVA)--differ with regard to safety and comfort. The criteria for the intraoperative safety and postoperative comfort of the patients were the incidents, events and complications (IEC) that required medical treatment as well as the evaluation of postoperative complaints by the patients according to the IEC list and patient questionnaires of the German Society of Anaesthesia and Critical Care Medicine (DGAI). METHODS. The study duration was about 4 months, from January to April 1992. During this period the patients of all nine operative departments of the hospital received strictly randomised NLA, BAL, or IVA. Patients who had regional anaesthesia or were not capable of understanding the German language, were nonco-operative, or were seriously ill (ASA class IV to V) as well as children under 18 years of age did not participate in the study. All eligible patients provided their informed consent. ANAESTHESIA. For premedication 10 mg chlorazepate was administered the night before and on the day of surgery. Anaesthesia was conducted under normoventilation using a mixture of 70% nitrous oxide and 30% oxygen. NLA patients were induced intravenously with 0.2 mg/kg body weight etomidate and received 0.005 mg/kg fentanyl and 0.07 mg/kg droperidol before the start of surgery. The repetition dose was 0.2 mg fentanyl and 2.5 mg droperidol. In the BAL patients the dose of fentanyl and droperidol was reduced to 50% due to the addition of isoflurane up to 1 vol. %. IVA patients received 2 mg/kg propofol over 3 min followed by an infusion of 3-5 mg/kg per hour together with 0.2 mg fentanyl/h. Neuromuscular blockade was accomplished with vecuronium 0.1 mg/kg. If the blood pressure and heart rate increased by more than 20% of preoperative values, analgesia was reinforced by an additional fentanyl dose. Anaesthesia was subsequently enhanced by increasing the neurolept/propofol/isoflurane dose by up to 50%. DATA COLLECTION. The following parameters were registered: patients' personal data and physical condition according to ASA classification; the grade of risk according to the Munich risk checklist; the frequency of IEC during surgery; the patients' permanent medications; postanaesthetic vigilance and recovery; the acceptance of the assigned anaesthetic by the physician; the cost of the anaesthetic used; and pre- and post-operative complaints as well as the assessment of anaesthesia by the patient. The statistical evaluation was performed using the chi-square test. RESULTS. A total of 1,346 patients were enrolled in the study; 28 (2%) were excluded because the treatment protocol was changed by the anaesthesiologist. Seventy per cent were recruited from general, gynaecologic, or otorhinolaryngologic surgery. The three anaesthetic regimens (NLA, BAL, and IVA) were used in other departments with the same frequency with the exception of ophthalmology and urology (P > 0.1) (Fig. 1). Of the 1,318 eligible patients, 443 received NLA, 443 BAL, and 432 IVA (P = 0.8). The distribution of the various parameters was surprisingly similar among the three groups: the average age was 50 years (P = 0.91), body weight 71 kg (P = 0.33), reference or initial blood pressure 130/80 mm Hg (P = 0.36), average time of anaesthesia 103 min (P = 0.82), and all had the same risk score (P = 0.42). Sixty per cent were female. An average of 85% of the 18- to 89-year-old patients were considered to be healthy according to the ASA risk classification (P = 0.42). However, on applying the Munich risk checklist the average number of healthy individuals was 5% to 10% lower than that of the ASA risk classification.

A comparative investigation of the metabolism of methyl bromide and methyl iodide in human erythrocytes

Human erythrocyte cytoplasm was incubated in head space vials with either methyl bromide or methyl iodide. The decline in concentration of the two methyl halides was monitored by gas chromatography. Simultaneously, the production of S-methylglutathione was determined by thin layer chromatography. In parallel experiments, boiled erythrocyte cytoplasm was used in order to determine non-enzymatic conjugation. Furthermore, inhibition experiments with sulfobromophthalein were performed. The results were compared with previous findings on the metabolism of methyl chloride. In contrast to methyl chloride, both methyl bromide and methyl iodide showed a significant non-enzymatic conjugation with glutathione. In addition, an enzymatic conjugation could be observed in the erythrocyte cytoplasm of the majority of the population, whereas a minority lacks this enzymatic activity. This is consistent with findings on methyl chloride. Inhibition experiments show that a minor form of the erythrocyte glutathione transferase may be responsible for the enzymatic conjugation. Of the three monohalogenated methanes, methyl bromide is the substrate with the highest affinity for the conjugating enzyme(s). In the case of methyl iodide, non-enzymatic reaction overweighs the enzymatic process. There are possible implications of the results for occupational health and the toxicity of the substances.

Experiences with a new corneal suction trephine

The importance of exact trephining for successful keratoplasty is well known. We employ a new suction trephine, thus obtaining exact and sharp cutting margines which are examined by scanning electron microscopy (SEM). The first observed clinical results in 25 cases are good.

Metabolism of methyl chloride by human erythrocytes

Erythrocyte cytoplasm of rats, mice and humans was incubated in head space vials with methyl chloride and the decline in concentration of the substance monitored as a parameter of metabolism. The production of S-methylglutathione was controlled by tlc. Rats, mice, bovines, pigs, sheep and rhesus monkeys showed no conversion of methyl chloride in erythrocyte cytoplasm. About 60% of the human blood samples showed a significant metabolic elimination of the substance (conjugators), whereas about 40% did not (non-conjugators). The production of S-methylglutathione indicated enzymatic metabolism of the substance by glutathione S-transferases. In literature, a "major" and "minor" form of human erythrocyte glutathione S-transferase has been described. The results indicate that the "minor" form is probably responsible for the unique metabolism of methyl chloride in human erythrocytes.

Concentration-dependent depletion of non-protein sulfhydryl (NPSH) content in lung, heart and liver tissue of rats and mice after acute inhalation exposure to butadiene

The effects of different exposure concentrations of butadiene on the cellular non-protein sulfhydryl (NPSH) content of liver, lung and heart tissue were investigated in B6C3F1 mice and Sprague-Dawley rats. Groups of male animals of both species were exposed for 7 h to 10, 50, 100, 250, 500, 1000 and 2000 ppm butadiene. Immediately after exposure, NPSH content of liver, lung and heart tissue was determined according to a modified Ellman procedure. A comparison of both species shows that a dose-dependent NPSH depletion can be observed in mice for all tissues examined. In rats, liver NPSH content shows a major reduction at high exposure concentrations only. In mice, depletion of NPSH content of liver, lung and heart tissue starts at exposure concentrations of about 250 ppm butadiene. A reduction in NPSH content of about 80% is observed for lung tissue at 1000 ppm and for liver and heart tissue at exposure concentrations of 2000 ppm butadiene. The data on tissue concentrations of NPSH obtained after exposure of rats and mice to butadiene reflect the quantitative differences in butadiene metabolism and in biological effectivity of reactive butadiene intermediates between both species.