AFM and FTIR Investigation of the Effect of Water Flow on Horseradish Peroxidase.

Atomic force microscopy (AFM)-based fishing is a promising method for the detection of low-abundant proteins. This method is based on the capturing of the target proteins from the analyzed solution onto a solid substrate, with subsequent counting of the captured protein molecules on the substrate surface by AFM. Protein adsorption onto the substrate surface represents one of the key factors determining the capturing efficiency. Accordingly, studying the factors influencing the protein adsorbability onto the substrate surface represents an actual direction in biomedical research. Herein, the influence of water motion in a flow-based system on the protein adsorbability and on its enzymatic activity has been studied with an example of horseradish peroxidase (HRP) enzyme by AFM, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and conventional spectrophotometry. In the experiments, HRP solution was incubated in a setup modeling the flow section of a biosensor communication. The measuring cell with the protein solution was placed near a coiled silicone pipe, through which water was pumped. The adsorbability of the protein onto the surface of the mica substrate has been studied by AFM. It has been demonstrated that incubation of the HRP solution near the coiled silicone pipe with flowing water leads to an increase in its adsorbability onto mica. This is accompanied by a change in the enzyme's secondary structure, as has been revealed by ATR-FTIR. At the same time, its enzymatic activity remains unchanged. The results reported herein can be useful in the development of models describing the influence of liquid flow on the properties of enzymes and other proteins. The latter is particularly important for the development of biosensors for biomedical applications-particularly for serological analysis, which is intended for the early diagnosis of various types of cancer and infectious diseases. Our results should also be taken into account in studies of the effects of protein aggregation on hemodynamics, which plays a key role in human body functioning.

Anterior Cruciate Ligament Ruptures in Russian Premier League Soccer Players During the 2010 to 2021/2022 Competitive Seasons: The Epidemiology and Details of Return to Sports.

Background: There are limited data on the epidemiology of anterior cruciate ligament (ACL) ruptures in elite adult soccer players, especially in the Russian Premier League (RPL). There is an increased risk of injury due to a combination of additional risk factors such as playing in extremely high and low temperatures, frequent long flights, and regular play on natural and artificial surfaces. Purpose: To study the epidemiology of ACL ruptures and determine the patterns associated with their occurrence in RPL soccer players. Study Design: Descriptive epidemiology study. Methods: All ACL ruptures requiring surgery sustained by players competing in the RPL across 12 competitive seasons between 2010 and 2022 were analyzed. All required data were collected from media analysis and confirmed by club doctors. Results: A total of 85 players sustained 100 injuries during 12 competitive seasons. A total of 96.5% of players returned to competitive play. The injury incidence in RPL and during participation of RPL teams in European Cups were 0.4760 and 0.5622 per 1000 playing hours, respectively. When analyzing the outcomes of the primary ACL surgery (a total of 76 operations), the following data were obtained: in 11 cases (14.5%), there was a reinjury on the ipsilateral knee joint and in 4 cases (5.3%) on the contralateral knee joint. The mean return-to-play time after all operations was 284 ± 116 days. The time of return to play after primary reconstruction was 289 ± 136 days, 278 ± 91 days after reconstruction on the contralateral knee and 271 ± 51.5 days after the first ACL revision reconstruction on the ipsilateral knee joints. Conclusion: RPL ACL injury epidemiology is similar to that in the other leagues from around the world, although there are factors that can potentially influence the number of these injuries.

The use of the first order system transfer function in the analysis of proboscis extension learning of honey bees, Apis mellifera L., exposed to pesticides.

No attempts have been made to apply a mathematical model to the learning curve in honey bees exposed to pesticides. We applied a standard transfer function in the form Y = B3*exp(- B2 * (X - 1)) + B4 * (1 - exp(- B2 * (X - 1))), where X is the trial number; Y is proportion of correct responses, B2 is the learning rate, B3 is readiness to learn and B4 is ability to learn. Reanalyzing previously published data on the effect of insect growth regulators tebufenozide and diflubenzuron on the classical conditioning of proboscis extension, the model revealed additional effects not detected with standard statistical tests of significance.

The Effect of a Dodecahedron-Shaped Structure on the Properties of an Enzyme.

In this research, the influence of a dodecahedron-shaped structure on the adsorption behavior of a horseradish peroxidase (HRP) enzyme glycoprotein onto mica substrates was studied. In the experiments, samples of an aqueous HRP solution were incubated at various distances (0.03 m, 2 m, 5 m, and control at 20 m) from the dodecahedron surface. After the incubation, the direct adsorption of HRP onto mica substrates immersed in the solutions was performed, and the mica-adsorbed HRP particles were visualized via atomic force microscopy (AFM). The effect of the increased HRP aggregation was only observed after the incubation of the enzyme solution at the 2 m distance from the dodecahedron. In addition, with respect to the control sample, spectrophotometric measurements revealed no change in the HRP enzymatic activity after the incubation at any of the distances studied. The results reported herein can be of use in the modeling of the possible influences of various spatial structures on biological objects in the development of biosensors and other electronic equipment.

Atomic Force Microscopy Study of the Effect of an Electric Field, Applied to a Pyramidal Structure, on Enzyme Biomolecules.

The influence of an external constant strong electric field, formed using a pyramidal structure under a high electric potential, on an enzyme located near its apex, is studied. Horseradish peroxidase (HRP) is used as a model. In our experiments, a 27 kV direct current (DC) voltage was applied to two electrodes with a conducting pyramidal structure attached to one of them. The enzyme particles were visualized by atomic force microscopy (AFM) after the adsorption of the enzyme from its 0.1 µM solution onto mica AFM substrates. It is demonstrated that after the 40 min exposure to the electric field, the enzyme forms extended structures on mica, while in control experiments compact HRP particles are observed. After the exposure to the electric field, the majority of mica-adsorbed HRP particles had a height of 1.2 nm (as opposed to 1.0 nm in the case of control experiments), and the contribution of higher (>2.0 nm) particles was also considerable. This indicates the formation of high-order HRP aggregates under the influence of an applied electric field. At that, the enzymatic activity of HRP against its substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) remains unaffected. These results are important for studying macroscopic effects of strong electromagnetic fields on enzymes, as well as for the development of cellular structure models.

AFM Investigation of the Influence of Steam Flow through a Conical Coil Heat Exchanger on Enzyme Properties.

The present study is aimed at the revelation of subtle effects of steam flow through a conical coil heat exchanger on an enzyme, incubated near the heat exchanger, at the nanoscale. For this purpose, atomic force microscopy (AFM) has been employed. In our experiments, horseradish peroxidase (HRP) was used as a model enzyme. HRP is extensively employed as a model in food science in order to determine the influence of electromagnetic fields on enzymes. Adsorption properties of HRP on mica have been studied by AFM at the level of individual enzyme macromolecules, while the enzymatic activity of HRP has been studied by spectrophotometry. The solution of HRP was incubated either near the top or at the side of the conically wound aluminium pipe, through which steam flow passed. Our AFM data indicated an increase in the enzyme aggregation on mica after its incubation at either of the two points near the heat exchanger. At the same time, in the spectrophotometry experiments, a slight change in the shape of the curves, reflecting the HRP-catalyzed kinetics of ABTS oxidation by hydrogen peroxide, has also been observed after the incubation of the enzyme solution near the heat exchanger. These effects on the enzyme adsorption and kinetics can be explained by alterations in the enzyme hydration caused by the influence of the electromagnetic field, induced triboelectrically by the flow of steam through the heat exchanger. Our findings should thus be considered in the development of equipment involving conical heat exchangers, intended for either research or industrial use (including miniaturized bioreactors and biosensors). The increased aggregation of the HRP enzyme, observed after its incubation near the heat exchanger, should also be taken into account in analysis of possible adverse effects from steam-heated industrial equipment on the human body.

The Effect of a Rotating Cone on Horseradish Peroxidase Aggregation on Mica Revealed by Atomic Force Microscopy.

Our study reported herein aims to determine whether an electromagnetic field, induced triboelectrically by a metallic cone, rotating at a frequency of 167 Hz, has an effect on the properties of the horseradish peroxidase (HRP) enzyme. Atomic force microscopy (AFM) was employed to detect even the most subtle effects on single enzyme molecules. In parallel, a macroscopic method (spectrophotometry) was used to reveal whether the enzymatic activity of HRP in solution was affected. An aqueous solution of the enzyme was incubated at a distance of 2 cm from the rotating cone. The experiments were performed at various incubation times. The control experiments were performed with a non-rotating cone. The incubation of the HRP solution was found to cause the disaggregation of the enzyme. At longer incubation times, this disaggregation was found to be accompanied by the formation of higher-order aggregates; however, no change in the HRP enzymatic activity was observed. The results of our experiments could be of interest in the development of enzyme-based biosensors with rotating elements such as stirrers. Additionally, the results obtained herein are important for the correct interpretation of data obtained with such biosensors.

AFM study of changes in properties of horseradish peroxidase after incubation of its solution near a pyramidal structure.

In our present paper, the influence of a pyramidal structure on physicochemical properties of a protein in buffer solution has been studied. The pyramidal structure employed herein was similar to those produced industrially for anechoic chambers. Pyramidal structures are also used as elements of biosensors. Herein, horseradish peroxidase (HRP) enzyme was used as a model protein. HRP macromolecules were adsorbed from their solution onto an atomically smooth mica substrate, and then visualized by atomic force microscopy (AFM). In parallel, the enzymatic activity of HRP was estimated by conventional spectrophotometry. Additionally, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) has been employed in order to find out whether or not the protein secondary structure changes after the incubation of its solution either near the apex of a pyramid or in the center of its base. Using AFM, we have demonstrated that the incubation of the protein solution either in the vicinity of the pyramid's apex or in the center of its base influences the physicochemical properties of the protein macromolecules. Namely, the incubation of the HRP solution in the vicinity of the top of the pyramidal structure has been shown to lead to an increase in the efficiency of the HRP adsorption onto mica. Moreover, after the incubation of the HRP solution either near the top of the pyramid or in the center of its base, the HRP macromolecules adsorb onto the mica surface predominantly in monomeric form. At that, the enzymatic activity of HRP does not change. The results of our present study are useful to be taken into account in the development of novel biosensor devices (including those for the diagnosis of cancer in humans), in which pyramidal structures are employed as sensor, noise suppression or construction elements.

Effect of Spherical Elements of Biosensors and Bioreactors on the Physicochemical Properties of a Peroxidase Protein.

External electromagnetic fields are known to be able to concentrate inside the construction elements of biosensors and bioreactors owing to reflection from their surface. This can lead to changes in the structure of biopolymers (such as proteins), incubated inside these elements, thus influencing their functional properties. Our present study concerned the revelation of the effect of spherical elements, commonly employed in biosensors and bioreactors, on the physicochemical properties of proteins with the example of the horseradish peroxidase (HRP) enzyme. In our experiments, a solution of HRP was incubated within a 30 cm-diameter titanium half-sphere, which was used as a model construction element. Atomic force microscopy (AFM) was employed for the single-molecule visualization of the HRP macromolecules, adsorbed from the test solution onto mica substrates in order to find out whether the incubation of the test HRP solution within the half-sphere influenced the HRP aggregation state. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was employed in order to reveal whether the incubation of HRP solution within the half-sphere led to any changes in its secondary structure. In parallel, spectrophotometry-based estimation of the HRP enzymatic activity was performed in order to find out if the HRP active site was affected by the electromagnetic field under the conditions of our experiments. We revealed an increased aggregation of HRP after the incubation of its solution within the half-sphere in comparison with the control sample incubated far outside the half-sphere. ATR-FTIR allowed us to reveal alterations in HRP's secondary structure. Such changes in the protein structure did not affect its active site, as was confirmed by spectrophotometry. The effect of spherical elements on a protein solution should be taken into account in the development of the optimized design of biosensors and bioreactors, intended for performing processes involving proteins in biomedicine and biotechnology, including highly sensitive biosensors intended for the diagnosis of socially significant diseases in humans (including oncology, cardiovascular diseases, etc.) at early stages.

The application of the first order system transfer function for fitting the California Verbal Learning Test learning curve.

Very few attempts have been made to apply a mathematical model to the learning curve in the California Verbal Learning Test list A immediate recall. Our rationale was to find out whether modeling of the learning curve can add additional information to the standard CVLT [corrected] measures. We applied a standard transfer function in the form Y = B3*exp(-B2*(X-1))+B4*(1-exp(-B2*(X-1))), where X is the trial number; Y is the number of recalled correct words, B2 is the learning rate, B3 is readiness to learn and B4 is ability to learn. The coefficients of the model were found to be independent measures not duplicating standard CVLT [corrected] measures. Regression analysis revealed that readiness to learn (B3) and ability to learn (B4) were significantly (p < .05) higher in a group of healthy participants than in a group of participants with type 2 diabetes mellitus (T2DM), but the learning rate (B2) did not differ (p > .2). The proposed model is appropriate for clinical application and as a guide for research and may be used as a good supplemental tool for the CVLT [corrected] and similar memory tests.

Children and adolescents' performance on a medium-length/nonsemantic word-list test.

Word-list learning tasks are among the most important and frequently used tests for declarative memory evaluation. For example, the California Verbal Learning Test-Children's Version (CVLT-C) and Rey Auditory Verbal Learning Test provide important information about different cognitive-neuropsychological processes. However, the impact of test length (i.e., number of words) and semantic organization (i.e., type of words) on children's and adolescents' memory performance remains to be clarified, especially during this developmental stage. To explore whether a medium-length non-semantically organized test can produce the typical curvilinear performance that semantically organized tests produce, reflecting executive control, we studied and compared the cognitive performance of normal children and adolescents by utilizing mathematical modeling. The model is based on the first-order system transfer function and has been successfully applied to learning curves for the CVLT-C (15 words, semantically organized paradigm). Results indicate that learning nine semantically unrelated words produces typical curvilinear (executive function) performance in children and younger adolescents and that performance could be effectively analyzed with the mathematical model. This indicates that the exponential increase (curvilinear performance) of correctly learned words does not solely depend on semantic and/or length features. This type of test controls semantic and length effects and may represent complementary tools for executive function evaluation in clinical populations in which semantic and/or length processing are affected.

A new mathematical model for assessment of memorization dynamics.

A new memory model is proposed based on regression analysis and exponential- shaped learning curves. The efficacy of the model is tested with several types of experiments including food aversion in snails, maze learning in rats and memory tests for adults and children. The model is also tested on drug abusers and alcoholics. The results of goodness of fit tests indicate that our model can accurately be used to predict the memory dynamics of diverse experiments and populations. The model can also be used to predict both group and individual performance. The application of the model to detect memory impairment is discussed, as are limitations.

The First Order Transfer Function in the Analysis of Agrochemical Data in Honey Bees (Apis Mellifera L.): Proboscis Extension Reflex (PER) Studies.

This paper describes a mathematical model of the learning process suitable for studies of conditioning using the proboscis extension reflex (PER) in honey bees when bees are exposed to agrochemicals. Although procedural variations exist in the way laboratories use the PER paradigm, proboscis conditioning is widely used to investigate the influence of pesticides and repellents on honey bee learning. Despite the availability of several mathematical models of the learning process, no attempts have been made to apply a mathematical model to the learning curve in honey bees exposed to agrochemicals. Our model is based on the standard transfer function in the form Y=B3 e(-B2 (X-1)) +B4(1-e(-B2 (X-1))) where X is the trial number, Y is the proportion of correct responses, B2 is the learning rate, B3 is readiness to learn, and B4 is ability to learn. We reanalyze previously published data on the effect of several classes of agrochemicals including: (1) those that are considered harmless to bees (e.g., pymetrozine, essential oils, dicofol); (2) sublethal exposure to pesticides known to harm honey bees (e.g., coumaphos, cyfluthrin, fluvalinate, permethrin); and (3) putative repellents of honey bees (e.g., butyric acid, citronella). The model revealed additional effects not detected with standard statistical tests of significance.

Pseudo ribbon metal ion beam source.

The paper describes high broad metal ion source based on dc macroparticle filtered vacuum arc plasma generation with the dc ion-beam extraction. The possibility of formation of pseudo ribbon beam of metal ions with the parameters: ion beam length 0.6 m, ion current up to 0.2 A, accelerating voltage 40 kV, and ion energy up to 160 kV has been demonstrated. The pseudo ribbon ion beam is formed from dc vacuum arc plasma. The results of investigation of the vacuum arc evaporator ion-emission properties are presented. The influence of magnetic field strength near the cathode surface on the arc spot movement and ion-emission properties of vacuum-arc discharge for different cathode materials are determined. It was shown that vacuum-arc discharge stability can be reached when the magnetic field strength ranges from 40 to 70 G on the cathode surface.

Plasma immersion ion charge state and mass spectrometer.

Investigation results of charge state of monocomponent plasma of Ti, Zr, W, and N, as well as that of multicomponent metal plasma of Ti/Zr (50/50 at.%) using plasma-immersion time-of-flight spectrometer are presented in the paper. The case of pressure impact in the working chamber on the ion charge state of combined metal (Ti) and gas-discharge (N) plasma is considered.

Overall Memory Impairment Identification with Mathematical Modeling of the CVLT-II Learning Curve in Multiple Sclerosis.

The CVLT-II provides standardized scores for each of the List A five learning trials, so that the clinician can compare the patient's raw trials 1-5 scores with standardized ones. However, frequently, a patient's raw scores fluctuate making a proper interpretation difficult. The CVLT-II does not offer any other methods for classifying a patient's learning and memory status on the background of the learning curve. The main objective of this research is to illustrate that discriminant analysis provides an accurate assessment of the learning curve, if suitable predictor variables are selected. Normal controls were ninety-eight healthy volunteers (78 females and 20 males). A group of MS patients included 365 patients (266 females and 99 males) with clinically defined multiple sclerosis. We show that the best predictor variables are coefficients B3 and B4 of our mathematical model B3 ∗ exp(-B2 ∗ (X - 1)) + B4 ∗ (1 - exp(-B2 ∗ (X - 1))) because discriminant functions, calculated separately for B3 and B4, allow nearly 100% correct classification. These predictors allow identification of separate impairment of readiness to learn or ability to learn, or both.

Assessment of the learning curve from the California Verbal Learning Test-Children's Version with the first-order system transfer function.

A mathematical model is proposed to measure the learning curve in the California Verbal Learning Test-Children's Version. The model is based on the first-order system transfer function in the form Y = B3*exp[-B2*(X-1)]+B4*{1-exp[-B2*(X-1)]}, where X is the trial number, Y is the number of recalled correct words, B2 is the learning rate, B3 is interpreted as readiness to learn and B4 as the ability to learn. Children's readiness to learn and ability to learn were lower than adults. Modeling revealed that girls had greater readiness to learn and ability to learn than boys.

Validity of the California Verbal Learning Test-II in multiple sclerosis.

Multiple sclerosis (MS) is a disease of the central nervous system where roughly 50% of patients exhibit cognitive impairment. Episodic memory defects are particularly common in MS and the California Verbal Learning Test: 2nd Edition (CVLT-II) was recommended for assessment in MS in a recently published consensus position paper. We investigated the validity of the CVLT-II in 351 MS patients and 69 demographically matched normal controls. MS patients performed significantly more poorly on 18 of the 23 measures examined. In addition to a general memory factor, factor analysis revealed five distinct factors conforming to measures of consolidation, primary/recency effect, proactive interference, and learning asymptote. The external validity of the CVLT-II was also supported by logistic regression analysis, which separated employed from work-disabled MS patients. We conclude that the CVLT-II is a valid test in MS and provides a rich constellation of verbal memory measures.

A new mathematical model for assessment of memorization dynamics

A new memory model is proposed based on regression analysis and exponential- shaped learning curves. The efficacy of the model is tested with several types of experiments including food aversion in snails, maze learning in rats and memory tests for adults and children. The model is also tested on drug abusers and alcoholics. The results of goodness of fit tests indicate that our model can accurately be used to predict the memory dynamics of diverse experiments and populations. The model can also be used to predict both group and individual performance. The application of the model to detect memory impairment is discussed, as are limitations (AU)

Se propone un nuevo modelo de memoria basado en el análisis de regresión y las curvas exponenciales de aprendizaje. La eficacia del modelo se verifica con varios tipos de experimentos incluyendo la aversión a la comida en caracoles, el aprendizaje de laberintos en ratas y las pruebas de memoria en adultos y niños. El modelo también se pone aprueba en drogadictos y alcohólicos. Los resultados de las pruebas de bondad de ajuste indican que nuestro modelo puede ser empleado con precisión para predecir las dinámicas de la memoria en diversos experimentos y poblaciones. También puede emplearse el modelo para predecir tanto la ejecución grupal como la individual. Se comenta la aplicación del modelo para detectar el deterioro de la memoria, así como las limitaciones del mismo (AU)

Diagnostico serologico de las leptospirosis y serotipos de leptospiras en Oriente-Norte

La prueba de aglutinacion y lisis de leptospiras, utilizando cepas certificadas de 16 serotipos causantes de las leptospirosis mas difundidas mundialmente, resulto positiva en 51 casos, comprobando el diagnositico y confirmando la existencia de infecciones por leptospira en Oriente-Norte