A Novel Approach in Heart-Rate-Variability Analysis Based on Modified Poincare Plots

Heart-rate variability (HRV), measured by the fluctuation of beat-to-beat intervals, has been growingly considered the most important hallmark of heart rate (HR) time series. The HRV can be characterized by various statistical measures both in the time and frequency domains, or by nonlinear methods. During the past decades, an overwhelming amount of HRV data has been piled up in the research community, but the individual results are difficult to reconcile due to the different measuring conditions and the usually HR-dependent statistical HRV-parameters applied. Moreover, the precise HR-dependence of HRV parameters is not known. Using data gathered by a wearable sensor of combined heart-rate and actigraphy modalities, here, we introduce a novel descriptor of HRV, based on a modified Poincare plot of 24-h RR-recordings. We show that there exists a - regressive biexponential - HRV versus HR "master" curve ("M-curve") that is highly conserved for a healthy individual on short and medium terms (on the hours to months scale, respectively). At the same time, we reveal how this curve is related to age in the case of healthy people, and establish alterations of the M-curves of heart-attack patients. A stochastic neuron model accounting for the observed phenomena is also elaborated, in order to facilitate physiological interpretation of HRV data. Our novel evaluation procedure applied on the time series of interbeat intervals allows the description of the HRV(HR) function with unprecedented precision. To utilize the full strength of the method, we suggest a 24-hour-long registration period under natural, daily-routine circumstances (i.e., no special measuring conditions are required). By establishing a patient's M-curve, it is possible to monitor the development of his/her status over an extended period of time. On these grounds, the new method is suggested to be used as a competent tool in future HRV analyses for both clinical and training applications, as well as for everyday health promotion

New trends in biophotonics

Photonic structures offer a promising alternative of conventional electronic ones, especially for future information technological applications. Instead of conductors and transistors, their optical analogues (miniature light guides and optical switches, respectively) are serving as passive and active elements processing information in photonic circuits. One of the biggest challenges in this respect is to find proper nonlinear optical (NLO) materials that are able to actively control the flow of information in integrated optical (IO) circuits. Several inorganic and organic materials have been considered for this special application, requiring high speed, sensitivity, reliability and log-term stability. So far, however, none of them is regarded as the optimal solution. In 2002, we suggested an especially stable, light-sensitive biomaterial, the protein bacteriorhodopsin (bR), to be used as an active material in NLO structures of IO applications (Ormos et al. 2002). An IO switching and modulation using a bR adlayer on a grating-coupled planar optical waveguide was also demonstrated. This publication inspired a number of upcoming research papers dealing with the application of bR in different optical switch structures, defining a new trend in photonics, using hybride structures comprised of passive inorganic, and active biomaterials. Below, we give a brief overview of the relevant, recent results

Biológiai membránok elektromos térszerkezetének vizsgálata = Investigation of the charge structure of biological membranes

A pályázat célja a biológiai membránok fizikai tulajdonságainak vizsgálata volt, különös tekintettel a töltéseloszlás és - ezzel összefüggésben - az elektromos térszerkezet funkcionális szerepére. Modellobjektumunk a protonpumpáló bakteriorodopszin (bR) fehérjét kristályos rendben tartalmazó bíbormembrán. Kutatásainkat és a velük kapcsolatos módszertani fejlesztőmunkát három téma köré csoportosítottuk: 1. A molekulán belüli elektromos töltéseloszlás funkcionális leírása 2. A határfelületi vízréteg szerepe a fehérjék szerkezetében és működésében 3. A bR nemlineáris optikai tulajdonságainak jellemzése Eredmények: 1.Megmutattuk, hogy az általunk kifejlesztett módszer a molekula működését kísérő szerkezetváltozásokat érzékenyen jellemzi, és lehetőséget teremt az elektromos töltésátrendeződések funkcionális értelmezésére. 2.Rámutattunk, hogy a semleges sók anionjainak tulajdonított Hofmeister-effektus a fehérje-víz határfelületi réteg szerkezetváltozásaival magyarázható. Elméletünk elsőként ad teljeskörű kvalitatív leírást a 120 éves problémakörre. 3.Integrált optikai módszerekkel az eddigieknél érzékenyebben detektáltuk a bR molekulában - a lokális elektromos tér változásai következtében ? fellépő abszorpció- és törésmutató-változásokat. Megmutattuk, hogy a molekula gerjesztését követő spektrális változások alkalmasak fénykapcsolásra és -modulálásra. Az eredmények gyakorlati alkalmazása az optoelektronikában és a bioszenzorikában várható. | In the framework of the project, we investigated some physical properties of biological membranes, with special respect to the physiological role of the electric charge distribution (hence the electric field structure). Our model object was purple membrane, containing the paradigmatic proton pumping molecule bacteriorhodopsin (bR) in a quasi crystalline structure. Our research work and the related methodological developments were centered round three topics: 1.Functional description of the intra-molecular charge distribution 2.The role of interfacial water in the structure and function of proteins 3.Characterization of the nonlinear optical properties of bR Results: 1.We showed that our method represents a sensitive test for the characterization of structural changes associated to molecular function, and allows interpretation of charge rearrangements. 2.We pointed out that the Hofmeister effect, attributed to the anions of neutral salts, can be interpreted according to structural changes in the protein-water interface. Our theory gives a full-spectrum qualitative description, solving a 120-years old puzzle. 3.Using integrated optical (IO) techniques, we could sensitively characterize the nonlinear optical properties of bR films, and showed that IO light switching and modulation can be performed based on the light-induced spectral changes of bR. Practical utilization of the results is expected in optoelectronics and sensorics

Photoactive Yellow Protein Adsorption at Hydrated Polyethyleneimine and Poly-l-Glutamic Acid Interfaces

This article was supported by the German Research Foundation (DFG) and the Open Access Publication Fund of Humboldt-Universität zu Berlin.Chiral and achiral vibrational sum-frequency generation (VSFG) spectroscopy was performed in the 1400–1700 and 2800–3800 cm−1 range to study the interfacial structure of photoactive yellow protein (PYP) adsorbed on polyethyleneimine (PEI) and poly-l-glutamic acid (PGA) surfaces. Nanometer-thick polyelectrolyte layers served as the substrate for PYP adsorption, with 6.5-pair layers providing the most homogeneous surfaces. When the topmost material was PGA, it acquired a random coil structure with a small number of β2-fibrils. Upon adsorption on oppositely charged surfaces, PYP yielded similar achiral spectra. However, the VSFG signal intensity increased for PGA surfaces with a concomitant redshift of the chiral Cα-H and N–H stretching bands, suggesting increased adsorption for PGA compared to PEI. At low wavenumbers, both the backbone and the side chains of PYP induced drastic changes to all measured chiral and achiral VSFG spectra. Decreasing ambient humidity led to the loss of tertiary structure with a re-orientation of α-helixes, evidenced by a strongly blue-shifted chiral amide I band of the β-sheet structure with a shoulder at 1654 cm−1. Our observations indicate that chiral VSFG spectroscopy is not only capable of determining the main type of secondary structure of PYP, i.e., β-scaffold, but is also sensitive to tertiary protein structure.National Research, Development and Innovation Office, HungaryEotvos Lorand Research NetworkDeutsche ForschungsgemeinschaftGerman Academic Exchange Service (DAAD)Eotvos Hungarian State Scholarship of Tempus Public Foundation funded by the Hungarian GovernmentPeer Reviewe

Mikromanipulációs kísérletek lézercsipesszel = Micromanipulation experiments with optical tweezers

A kutatás az optikai mikromanipuláció területén, különböző irányokban végzett fejlesztéseket és kutatási alkalmazásokat képviselt. A mikromanipuláció területén azt vizsgáltuk, milyen új manipulációs lehetőségeket nyújtanak speciális alakú próbatestek (ellentétben az általáéban használt gömb alakkal). Ennek során kidolgoztuk a lézeres fotopolimerizációs struktúra építés technikáját. Ezzel egyrészt a mikromanipuláció új lehetőségeit vizsgáltuk. Például, lehetőség nyílik torziós manipulálásra, csavarásra, meghatároztuk a DNS molekula torziós rugalmasságát. Ezen kívül, bonyolult struktúrákat építettünk, fénnyel hajtott mikrogépeket, mikrofluidikai csatornákat, integrált optikai szenzorokat. Ezekből bonyolultab összetett rendszereket raktunk össze: fénnyel vezérelt fluorescencia aktivált optikai sejtszeparátort. Kidolgoztuk a fénnyel vezérelt elektroozmózis eljárását. Itt elektromos térrel mozgatott folyadék áramlását vezéreljük fénnyel, ez érdekes jelenség, és új lehetőségeket nyújt mikrofluidikai rendszerek vezérlésében. | The research represented studies in the area of optical micromanipulation, both developing new procedures and basic applications. In the area of micromanipulation we investigated, what new possibilities are offered by test objects of special shapes (as opposed to the generally used spheres). In this process we developed the structure building by laser induced photopolymerization. With this we studied new possibilities of optical manipulation. For example, a poissibility emerges for torsional manipulation, twisting, we determined the torsional elasticity of DNA molecules. In addition, we built complex structures, light driven micromachines, microfluidics channels, integrated optical sensors. From this we constructed complex systems, e.g. a fluorescence activated cell separator. We developed the method of optically controlled electroosmosis. Here the fluid is driven by electric field and this is controlled by light. This is an interesting phenomenon, and is opens new possibilities in the control of microfluidics systems

Biological Microscopy with Undetected Photons

Novel imaging techniques utilizing nondegenerate, correlated photon pairs sparked intense interest during the last couple of years among scientists of the quantum optics community and beyond. It is a key property of such "ghost imaging" or "quantum interference" methods that they use those photons of the correlated pairs for imaging that never interacted with the sample, allowing detection in a spectral range different from that of the illumination of the object. Extensive applications of these techniques in spectroscopy and microscopy are envisioned, however, their limited spatial resolution to date has not yet supported real-life microscopic investigations of tiny biological objects. Here we report a modification of the method based on quantum interference by using a seeding laser and confocal scanning, that allows the improvement of the resolution of imaging with undetected photons by more than an order of magnitude, and we also present examples of application in the microscopy of biological samples.Comment: This article has been accepted for publication in IEEE Access, but has not been fully edite

Hydrogen peroxide contributes to the ultraviolet-B (280-315 nm) induced oxidative stress of plant leaves through multiple pathways

Solar UV-B (280-315 nm) radiation is a developmental signal in plants but may also cause oxidative stress when combined with other environmental factors. Using computer modelling and in solution experiments we show that UV-B is capable of photosensitizing hydroxyl radical production from hydrogen peroxide. We present evidence that the oxidative effect of UV-B in leaves is at least two-fold: (i) it increases cellular hydrogen peroxide concentrations, to a larger extent in pyridoxine antioxidant mutant pdx1.3-1 Arabidopsis and (ii) is capable of a partial photo-conversion of both ‘natural’ and ‘extra’ hydrogen peroxide to hydroxyl radicals. As stress conditions other than UV can increase cellular hydrogen peroxide levels, synergistic deleterious effects of various stresses may be expected already under ambient solar UV-B