Ion detector of time-of-flight mass spectrometer with registration of leading and trailing edges

The accuracy of the ion flight time measurement in the time-of-flight mass spectrometer is critical to achieving high resolution. The pulse amplitude variation of the detector pulses leads to the registration time spread at a given pulse detection threshold. This time spread can be eliminated by determining the position of the pulse apex. To determine the position of the pulse apex, the output of the ion detector is fed simultaneously to the two channels of the time-to-digital converter. In this case, the first channel is set to register the leading edge, and the second channel is set to register the trailing edge of the pulse. Using a simple processing of the received data, the position of the pulse tip is determined. Thus, the dependence of the temporal position of the peak on the pulse amplitude is largely eliminated. Examples are given, and the efficiency of using this algorithm to increase the resolution of time-of-flight mass spectral peak registration is demonstrated.

Production and Characterization of Photorin, a Novel Proteinaceous Protease Inhibitor from the Entomopathogenic Bacteria Photorhabdus laumondii

Entomopathogenic bacteria of the genus Photorhabdus secrete protease S (PrtS), which is considered a virulence factor. We found that in the Photorhabdus genomes, immediately after the prtS genes, there are genes that encode small hypothetical proteins homologous to emfourin, a recently discovered protein inhibitor of metalloproteases. The gene of emfourin-like inhibitor from Photorhabdus laumondii subsp. laumondii TT01 was cloned and expressed in Escherichia coli cells. The recombinant protein, named photorin (Phin), was purified by metal-chelate affinity and gel permeation chromatography and characterized. It has been established that Phin is a monomer and inhibits activity of protealysin and thermolysin, which, similar to PrtS, belong to the M4 peptidase family. Inhibition constants were 1.0 ± 0.3 and 10 ± 2 µM, respectively. It was also demonstrated that Phin is able to suppress proteolytic activity of P. laumondii culture fluid (half-maximal inhibition concentration 3.9 ± 0.3 nM). Polyclonal antibodies to Phin were obtained, and it was shown by immunoblotting that P. laumondii cells produce Phin. Thus, the prtS genes in entomopathogenic bacteria of the genus Photorhabdus are colocalized with the genes of emfourin-like inhibitors, which probably regulate activity of the enzyme during infection. Strict regulation of the activity of proteolytic enzymes is essential for functioning of all living systems. At the same time, the principles of regulation of protease activity by protein inhibitors remain poorly understood. Bacterial protease-inhibitor pairs, such as the PrtS and Phin pair, are promising models for in vivo studies of these principles. Bacteria of the genus Photorhabdus have a complex life cycle with multiple hosts, being both nematode symbionts and powerful insect pathogens. This provides a unique opportunity to use the PrtS and Phin pair as a model for studying the principles of protease activity regulation by proteinaceous inhibitors in the context of bacterial interactions with different types of hosts.

NMR assignments and secondary structure distribution of emfourin, a novel proteinaceous protease inhibitor

Emfourin (M4in) from Serratia proteamaculans is a new proteinaceous inhibitor of protealysin-like proteases (PLPs), a subgroup of the well-known and widely represented metallopeptidase M4 family. Although the biological role of PLPs is debatable, data published indicate their involvement in pathogenesis, including bacterial invasion into eukaryotic cells, suppression of immune defense of some animals, and destruction of plant cell walls. Gene colocalization into a bicistronic operon observed for some PLPs and their inhibitors (as in the case of M4in) implies a mutually consistent functioning of both entities. The originality of the amino acid sequence of M4in suggests it belongs to a previously unknown protein family and this encourages structural studies. In this work, we report a near-complete assignment of 1H, 13C, and 15N resonances of recombinant M4in and its structural-dynamic properties derived from the chemical shifts. According the NMR data analysis, the M4in molecule comprises 3-5 helical elements and 4-6 β-strands, at least two of which are apparently antiparallel, ascribing this obviously globular protein to the α + β structural class. Besides, two disordered regions also exist in the central loops between the regular secondary structural elements. The obtained data provide the basis for determining the high-resolution structure as well as functioning mechanism of M4in that can be used for development of new antibacterial therapeutic strategies.

Synthesis and characterization of heteroleptic rare earth double-decker complexes involving tetradiazepinoporphyrazine and phthalocyanine macrocycles

Reaction of (2,3,9,10,16,17,23,24-octabutylphthalocyaninato)lanthanide(iii) acetylacetonates (BuPcLn(acac), 1a-c, Ln = Lu (a), Eu (b), La (c)) with a tetrakis(5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazine ligand (tBuPhDzPzH2, 2) produced sandwich compounds (tBuPhDzPz)Ln(BuPc) (3a-c), which represent the first heteroleptic double-deckers incorporating both Pc and DzPz decks. A combination of high-resolution mass spectrometry, UV-Vis/NIR, MCD, and 1H NMR spectroscopy, and square-wave voltammetry provided unambiguous characterization of target complexes 3 indicating that their spectral and electrochemical properties are generally intermediate with respect to their homoleptic relatives. Based on the data of solution-state 1H-1H NMR (COSY, NOESY) correlation spectroscopy supported by DFT calculations, a dimerization tendency of compounds 3 proportional to the Ln(iii) ion size was found. The spectroelectrochemical study of 3 and the corresponding homoleptic double-deckers revealed a pronounced tendency to aggregation of the one-electron oxidized forms of DzPz-containing double-decker complexes compared to homoleptic Pc2Ln compounds.

Ionization of organic molecules with metal ions formed in the laser plasma

A laser plasma ion source was used to ionize volatile organic compounds in a gas sample. The plasma was generated on a metal target in the intermediate vacuum region of ~0.3 Torr using a pulsed Nd:YAG laser with a wavelength of 1 μm. The resulting ions mass spectra were acquired using orthogonal time-of-flight mass spectrometer (O-TOF MS). When using a copper target, the ions formed are simple complexes (CuM⁺ ) of copper ions with organic molecules. The possibility of online identification of trace amounts of alkanes in nitrogen and air, with a detection limit of ~10 ppb, was demonstrated. The ionization efficiency of volatile organic compounds through the formation of clusters with metal ions is 10^-4 in terms of the quasimolecular complex ions. The rate constants of ion-molecular reactions of copper ions with octane and water molecules in nitrogen and air are estimated.

Note: Isolated high-voltage thermo-compensated DC power supply for mass spectrometry

The design of a highly stable isolated high voltage power supply is proposed and developed. The power supply is characterized by good temperature stability (<15 ppm/°C) and very low ripple level (<7 ppm) which were reduced by using a sinusoidal voltage in the transformer conversion. We anticipate that the power supplies of this type can find their utility in modern high-resolution mass spectrometers, particularly in time-of-flight and Orbitrap-type instruments providing a high resolution of ∼100 000 FWHM and high accuracy of m/z determination.

[Photomatrix LED therapy in patients with post-stroke arthropathy of the shoulder joint]

AIM

To assess the impact of quasi-monochromatic partially coherent infra-red radiation on the dynamics of recovery of the affected joint and the hemostatic system in patients with post-stroke arthropathy of the shoulder joint.

MATERIAL AND METHODS

Fifty-five patients in the early, late and residual period of ischemic stroke were studied. Group I consisted of 27 patients who underwent 10 sessions of photomatrix therapy (wavelength 600 nm) on the affected joint, lasting for 10 minutes. In patients of group II (n=28), the duration of photomatrix therapy was 20 minutes. Patients of the comparison group (n=20) did not receive photomatrix therapy.

RESULTS AND CONCLUSION

The results pointed to a significant reduction in the severity of pain, increase in the range of motion in the shoulder joint. All this was combined with a decrease in the severity of anxiety and depression, followed by a mild hypocoagulation effect and improvement of blood circulation in the paretic limb. The authors point out to the prospect of using this method for the prevention and treatment of post-stroke arthropathy.

[CLINICAL ASPECTS OF SEPTIC ENCEPHALOPATHY]

Septic encephalopathy is a form of general cerebral dysfunction caused by a systemic inflammatory reaction. Its investigation encounters enormous difficulties for the lack of reliable biological markers of neuronal lesions and methods for the evaluation of consciousness in severely ill patients. Hence, the importance of correct clinical interpretation of the character and magnitude of CNS activity. Examples are presented demonstrating the difficulty of interpreting disorders in CNS activity associated with evere community-acquired pneumonia.

[Study of changes in the enzyme-salt composition affecting the permeability of ocular tissues under infrasound phonophoresis]

This paper deals with the study of infrasound phonophoresis-induced changes in biochemical factors, which affect the permeability of eyeball tissues. During 10 days, the rabbit right eye was exposed to an infrasound in the changing pressure mode at 4 Hz and 173 dB for 10 minutes every day. The left eye remained control. After finishing a series of studies, the animals were slaughtered, the eyes were enucleated and prepared into individual tissues. Changes in sodium-potassium composition were investigated in the first series. By causing a reduction in the cellular content of K+, infrasound exposure was found to cause a decrease in membranous potential and activation Na-channel, as confirmed by the elevated intracellular levels of Na+. This in turn enhances ocular tissue permeability for drugs without damaging the structure of a cell membrane. Changes in the activity of the following enzymes: beta-glucosidase, cathepsin D, and hy- aluronidase. Infrasound was ascertained to enhance the activity of beta-glucosidase, which accounts for the lower levels of glucose in ocular tissues and points to the activation and acceleration of biochemical processes in the tissues. At the same time the increased concentrations of cathepsin D and hyaluronidase found in ocular tissues were responsible for a temporary reduction in the viscosity of hyaluronic acid, which promotes resolution of opacities, adhesions or scars and increased tissue permeability.

[Electron-microscopic changes of the brain in acute experimental peritonitis (AEP)]

It is shown that changes in the vessels of the central nervous system, neurons and interneuron links--synapses develop in AEP. Increasing diffuse-focal destructive brain changes are morphological substrate of toxico-hypoxic encephalopathy and basis for disturbances of an integrative-trigger action of the brain.

[Morphology and morphogenetic mechanisms of brain lesions in acute generalized peritonitis]

Pronounced alterations of brain elements (vessels, neurocytes, glial cells, neural fibers and synaptic apparatus) are observed in acute generalized peritonitis. The following morphological forms of peritoneal encephalopathy were recognized: diffuse-focal lesions, incomplete partial necroses, inflammatory changes in the form of meningitis and encephalitis. The morphological changes were provoked by some factors resultant from developing endotoxicosis and homeostatic disorders. Structural disturbances may play a leading role in polyorganic insufficiency and under certain conditions may have an independent tanatogenetic significance.

[Structure of lethal outcomes of combat trauma occurred on a battlefield during the war in the Northern Caucasus]

A clinico-anatomical analysis of lethal outcomes in combat trauma allows judging about the level of organization and quality of first aid at battlefield. The investigation showed that under conditions of modern military conflicts the wounds are grave, in many cases compound and multiple. The wounds are often located on the head, chest, abdomen and lower limbs, prevailing causes of death--lethal trauma and bleeding. The results of this study show the necessity of perfecting organization and quality of the first aid at the battle field and of providing the military with modern efficient accident preventatives.

[Urgent problems of medical aid in infectious endocarditis]

The authors analyze the incidence of infectious endocarditis (IE), the influence of diagnostic time on the lethality, the significance of surgical treatment. The main ways of further improvement of IE patient therapy are defined. They include the training of medical staff, centralization of the patients in the military medical institutions of the center by transfer from the districts after making the diagnosis in order to conduct the adequate medicamentous and appropriate surgical treatment.

[Experimental study of infrasonic phonophoresis]

A new method of drug administration, infrared phonophoresis, was experimentally studied. The method has no analogs in the world. The study was carried out on 20 Chinchilla rabbits. Water applications impregnated with equal volumes of the radiopharmaceutical (RP) were placed into the conjunctival cavities of both eyes. The right eye was control and the left was treated by infrasound (experiment). The information was recorded in live animals after removal of the application and thorough washing of the conjunctival cavity immediately, 30 min, and 1 h after infrasound phonophoresis session. Radioactivity measurements at all terms indicate its stable increase in the experimental eye and a progressive decrease in the control eye. Hence, infrasound promoted long accumulation of the RP in the eye at anterior route of the drug delivery without preliminary injection of the drug into ocular vessels.

[Clinical assessment of infrasonic phonophoresis efficacy in the treatment of bacterial keratitis]

Therapeutic efficacy of infrasonic phonophoresis is studied in 30 patients with bacterial keratitis. Control group consisted of 87 patients with the same diagnosis. Clinical studies included comparative evaluation of the therapeutic efficacy of infrasonic phonophoresis and traditional local instillations of the same drugs. Before treatment, visual acuity was the same in both groups, while after regression of inflammation after treatment it was 0.13 higher in the phonophoresis group. Results of clinical studies indicate a higher efficacy of infrasonic therapy of patients with keratitis. The duration of therapy was decreased, number of bed-days decreased, and visual acuity after treatment improved.

Effects of 50% ethanol and mechanical epithelial debridement on corneal structure before and after excimer photorefractive keratectomy

PURPOSE

The corneal epithelium is generally removed before photoablation in photorefractive keratectomy (PRK) because laser transepithelial PRK may result in surface irregularity caused by variability in epithelial thickness and differing ablation rates between epithelium and stroma. We compared the effects of mechanical deepithelialization with chemical epithelial removal by using 50% ethanol on the corneal structure.

METHODS

Fourteen rabbits underwent corneal deepithelialization by using a blade in the left eye and 24 h later in the right eye. Another 14 rabbits underwent corneal deepithelialization by using 50% ethanol solution. Half of the eyes treated with each technique underwent PRK after deepithelialization. Pachymetry was performed before and after each procedure on right eyes. Keratocyte and neutrophil densities were assessed by light microscopy.

RESULTS

Among non-laser-treatment groups, eyes that underwent mechanical deepithelialization had decreased corneal thickness (p = 0.001), increased keratocyte densities (p = 0.03), and no significant difference in neutrophil densities (p = 0.91) compared with chemically treated eyes 24 h after surgery. Among laser-treatment groups, eyes that underwent mechanical epithelial removal had increased keratocyte densities (p = 0.001), decreased corneal thickness (p = 0.03), and increased neutrophil densities (p = 0.03) 24 h after surgery compared with chemically treated eyes.

CONCLUSION

Deepithelialization with 50% ethanol causes more keratocyte loss with perhaps more corneal edema, but less stromal influx of neutrophils, than does a mechanical technique 24 h after PRK in a rabbit model. Corneal deepithelialization with dilute ethanol may be a viable option in PRK. However, further investigation into the safety of this technique is warranted before it can be widely applied clinically.