Fluorescent properties of surface tissues of apples of different varieties in the green area of spectrum

Background: Traditional methods of the content and composition of fruits nutrients determining are labor-intensive and material-intensive, require grinding and special processing of biological material. The fluorescent method is one of the most modern and promising. It allows determining physiological and metabolic parameters without plant tissues destruction. Therefore, the patterns and causes of differences identification of the different apple varieties fluorescent properties is an important task, which will solve the problem of non-invasive determination of the composition and content of useful substances in fruits. Objectives: The determination of the surface tissues fluorescent properties in the green area of the fluorescence spectrum of apple varieties with different coloring of exocarp is the purpose of the work. Materials and methods: The object of the study is apples of four popular winter varieties, close in maturity, with different coloring of exocarp. The method of fluorescence spectroscopy of the apples surface tissues was used. The excitation was made by a semiconductor laser with a wavelength of 405 nm and a power of 36 mW, operating in a continuous mode. The apples coloring is defined as the coordinate a of the CIELAB color mapping system. Results: It was found that the wavelength of the maximum in the green area of the fluorescence spectrum of different apple varieties surface tissues differs by approximately 8–18 nm. At the same time, the difference of wavelengths of the maximum in the red area for different apple varieties does not exceed 5 nm. It was found that wavelength of the maximum in the green area of the fluorescence spectrum differs in different varieties in accordance with the coloring of the exocarp. If green color prevails in the exocarp coloring the fluorescence maximum in the green area has a longer wavelength, and if red prevails it has a shorter wavelength, while if yellow prevails, the wavelength occupies an intermediate position. Conclusions: The pigment composition of the surface tissues of apples affects on their fluorescence in the green area of the spectrum. Possible reasons for the differences of the maximum wavelength in the green area of the fluorescence spectrum are the variability of flavonols composition depending on the apple variety and the influence of red pigments.

A Note on the Consequences of a Hot Mitochondrion: Some Recent Developments and Open Questions

Background: Chrétien and co-workers (PLOS Biology. 2018;16(1):e2003992) recently suggested that the mitochondrion might possibly be hotter than its surrounding (by as much as 10°C). Objectives: To examine the validity of this claim and review the possible implications and repercussion of such a claim – if true – on some aspects of mitochondrial biochemistry and biophysics. Results: Both the chemical gradient and the electrical gradient Gibbs energy terms in the central equation of chemiosmotic theory are temperature dependent, the first explicitly and the second implicitly. A hotter mitochondrion – as claimed – would imply a 3% correction in the chemical gradient term, but we cannot estimate the corresponding effect on the electrical term at this time since the functional dependence of the voltage on the temperature is not known to the best of the authors’ knowledge. Further, if this claim is true and to the extent claimed (10°C), this may imply some heat-engine character for mitochondrial thermodynamic operation albeit this may only represent 4% at most. Conclusions: Doubts and criticisms regarding the suggestion of a hotter mitochondrion have been raised and are briefly discussed. These doubts are contrasted with some data and considerations that support the claim of a hotter mitochondrion. It is concluded that the mitochondrion is probably hotter than its environment but not to the extent claimed by Chrétien et al. and that the thermodynamic efficiency and the mode of operation of the mitochondrion as an electrochemical battery are very slightly perturbed by even the maximum claimed revision of the temperature of its operation.

Influence of cellulose particles on chemical resistance, mechanical and thermal properties of epoxy composites

Background: The technological developments for nanocellulose production from cheaper plant materials compared to wood, in particular, agricultural waste is an urgent task of nanobiophysics. The discovery of possibility of expanding the functional characteristics of materials in compositions with modified cellulose particles essentially stimulated the interest of researchers in cellulose composites. Surface modification of cellulose particles by functional materials, such as dyes, metal oxides, silicon, allows applying composites with modified cellulose in various areas of modern industry. A significant improvement in the operational performances of functionalized cellulose particles can be achieved by using them as filler in polymers. Epoxy resin compositions with modified and unmodified cellulose particles, studied in present work, are an example of hybrid biosystem. The interfacial interaction of filler particles with the epoxy matrix, their concentration and dispersion can change the physical and chemical properties of the biopolymer and the functional parameters of biocomposites. Studying the influence of external fields on the physical and chemical properties of epoxy resin-based biosystems and their influence on operational parameters seems to be an urgent problem of advanced and sustained materials science. Objectives: The purpose of this work was to develop an effective nanocellulose synthesis from plant materials and surface functionalization of micro- and nanocellulose particles with clathrochelate iron (ΙΙ) dye as well obtaining biocompositions of epoxy resin with functionalized and non-functionalized micro- and nanocellulose, and to explore of the morphology, chemical resistance, mechanical and thermal properties of epoxy composites with cellulose micro and nanoparticles. Materials and methods: The studying objects were the composites of epoxy resin Eposir-7120 with a polyethylene polyamine “PEPA” hardener in a ratio of 6.2:1 and 10% cellulose micro and nanoparticles. The microcellulose obtained from wood has been a commercial product. Nanocellulose has been synthesized from organosolv cellulose obtained from Miscanthus x giganteus stalks. Surface modification of micro- and nanocellulose was performed using the clathrochelate iron (ΙΙ) dye. The specific surface area of cellulose particles was determined using low-temperature nitrogen adsorption-desorption according to the Brunauer-Emmett-Teller method. Mechanical parameters were determined using universal Shopper and UMM-10 machines. Thermal analysis was performed using Q1500 analyzer. Swelling was determined by the gravimetric method. Results: Elastic modulus E, compressive strength σ and thermogravimetric parameters were determined. It was shown that in composites with micro and nanocellulose the E rises in 7.0–12.2% while the σ increases in 9.1% for composites with cellulose micro particles. The loading resin with nanocellulose and modified cellulose microparticles no affects the σ value of composites. The thermal stability of epoxy polymer (310°C) reduces after loading with micro and nanocellulose to 290 and 300°C, respectively. Chemical resistance of composites with both celluloses to 20% nitric acid reduces. In neutral medium swelling characterizes by rapid sorption to saturation of 15–20% acetone in 36 hours. Conclusions: Thus, the synthesis method of nanocellulose from plant materials and functionalization of its surface with clathrochelate iron (ΙΙ) were developed. Light response of dye was detected in visible spectral range. Epoxy resin composites with 10% micro and nanocellulose were obtained. The filling effect with micro- and nanocellulose at elastic modulus, compressive strength, and thermal stability of epoxycomposites was studied. The swelling processes run similarly in composites with cellulose micro and nanoparticles.

Synthesis and properties of SiO2 photonic crystals modified by DNA

Background: Photonic crystals are structures characterized by periodic modulations of the refractive index with a period commensurate with the wavelength. This periodicity is associated with the existence of a complete band gap in the spectrum of the electromagnetic states of the crystal. The stop zone is called the band gap for the highlighted direction in the crystal. Globular photonic crystals are called three-dimensional photonic crystals, which consist of the same diameter globules. The pores between the globules in the opal allow one to change the refractive index and optical contrast of the material. The task of controlling the stop-zone frequency limits of a globular photonic crystal without changing its physical structure is of practical interest. The easiest way to control the stop-zone parameters is to fill the pores of the photonic crystals with materials with different refractive indices, for example, DNA. Control of the optical parameters of a globular photonic crystal can be used for the creation of optical detectors, sensors, test systems, a quantum biocomputer as well as analyzing and studying a conformational state of DNA. Objectives: the creation of SiO2 globular photonic crystals modified by DNA and studying of the influence of DNA on their optical properties. Materials and Methods: Ethyl alcohol, distilled water, ammonium hydroxide, tetraethoxysilane and DNA were used to synthesize SiO2 photonic crystals. Aqueous DNA solution was used to infiltrate the photonic crystals. We used a visible range spectroscopy for optical experiments and a finite-difference time-domain (FDTD) method for numerical calculations. Results: SiO2 globular photonic crystals modified by DNA were synthesized with 195 nm globules. The reflection spectra of the obtained photonic crystals were measured. A red-shift of the stop-zone maximum after the infiltration of photonic crystals with DNA molecules was found. The electric field distribution was calculated for the photonic crystal with 200 nm globules. Conclusions: FDTD calculations in the linear mode show that the presence of point defects in the structure of the photonic crystal influences the amplification of the local electric field in the interglobular space of the photonic crystal, which houses the DNA molecule at infiltration. The DNA infiltration into the pores of a photonic crystal changes the effective refractive index of the system by 5.99%. Synthesis SiO2 photonic crystals with DNA leads to the formation of a more ordered structure at the macro levels. Thus, DNA serves as a template-like structure for photonic crystals to be assembled on. In this case, the effective refractive index of the system increases by 6.01%.

Spectral and structural features of bio-composite films of graphene oxide and molybdenum disulphide with molecules of 5-bromouracyl and 5-bromo-2’-deoxyuridine

Background: Recently, composite materials based on nanoparticles and biological molecules have been intensively studied due to the unique physicochemical and biophysical properties and prospects of application in various fields of technology, engineering and medicine. Many laboratories conduct experiments with composite materials based on carbon nanoparticles and various 2D nanomaterials in order to create sensitive biosensors based on them, to develop new functional materials for biology and medicine. A wide range of practical applications requires fundamental knowledge about the structure of the created composites, the interaction energy between the components and their spectral characteristics. Objectives: The purpose of the work was to study the structural features of biocomposite films of graphene oxide (GO) and molybdenum disulfide MoS2 with 5-bromouracil (5BrU) and 5-bromo-2'-deoxyuridine (5BrdU) and to obtain information on the interaction between their components based on data from the infrared Fourier spectroscopy and quantum chemical calculations. Materials and methods: For the measurements, a vacuum infrared Fourier spectrometer was used. The composite films were created by the drop casting method based on graphene oxide from GRAPHENEA, an aqueous suspension of MoS2 molybdenum disulfide powder, as well as 5BrU and 5BrdU biomolecules. For the quantum-chemical calculations of model structures the Gaussian 09 and the Firefly 8.0 programs were used. In last one the GAMESS (USA) program code was partially used. Results: The frequencies and intensities of infrared absorption bands of the biocomposite films (5BrU/GO, 5BrU/MoS2, 5BrdU/GO and 5BrdU/MoS2) with different numbers of biomolecules were obtained. The absorption bands of composite films are assigned to the corresponding types of normal vibrations. The interaction energies in model structures are determined. The amorphous (disordered) structure of 5BrU clusters in 5BrU/GO composites at a low concentration of biomolecules has been established. It is shown that the MoS2 composites are more heterogeneous than the GO composites. Conclusions: The absorption band of CO vibrations with a frequency of 1783 cm–1 as well as the bands of the out-of-plane deformation vibrations γNH of 5BrU are sensitive to the structure of 5BrU clusters in composite films. It has been demonstrated that graphene oxide in the composite films affects the conformational equilibrium of 5BrdU. It has been established that structures with stacking between the pyrimidine ring of a nucleoside and the basal plane of graphene oxide are the most energetically favorable.

Influence of components of optical momentum and spin of evanescent waves on micro- and nanoobjects (Review)

Background: Mechanical properties of light are widely used in applied areas, such as optical trapping and manipulation, sorting, deformation of biological cells and molecules. In general, the evanescent field may exhibit three components of optical momentum and spin angular momentum (spin), which manifest themselves in the occurrence of corresponding components of optical force and torque. Such extraordinary properties of evanescent waves open up new possibilities for manipulating of micro- and nanoobjects, in comparing with classical optical tweezers and manipulators, which can be used for solving the applied problems, in particular, of biomedicine. Objectives: Aim of this work is to analyze and summarize recent studies regarding to the mechanical influence of evanescent field on micro- and nanoobjects, in particular, related to the influence of transverse components of optical momentum and spin. Materials and methods: Method of momenta allows one to distinguish in an evanescent field the action of optical forces and torques, associated with the components of optical momentum and angular momentum of different nature and action direction, depending on the polarization of the incident wave. Experimental methods of particle manipulation in the near field allow visualizing such an influence, which makes it possible for solving the applied problems. Results: Recent studies demonstrate the action on nano- and microobjects of such "extraordinary" optical momentum and spin components, as transverse spin momentum, transverse spin, transverse imaginary optical momentum component, and vertical spin. Using, in particular, the latter, to solve the applied problems of biomedicine is proposed, such as transporting of therapeutic agents to pathological areas or restoring vascular patency and tissue blood supply. Conclusions: Obtained results of theoretical and experimental investigation of the mechanical action of the optical momentum and spin components of evanescent field allow us to extend the approaches of optical manipulation of micro- and nanoobjects, with the possibility of applications, in particular, for the problems of biomedicine.

Mass spectrometry study of noncovalent complexes formation of antibiotic cycloserine with N-acetyl-D-glucosamine and ascorbic acid

Background: While antibiotic cycloserine (CYS) is widely applied in the treatment of tuberculosis, our knowledge of the drug intermolecular interactions with targeting biomolecules and other drugs remains incomplete. It is believed that the CYS antibacterial activity is related to inhibiting the bacterial cell wall biosynthesis. On the other hand, intermolecular interactions of CYS with ascorbic acid (ASC) molecules is worth of studying taking into account that ASC can be used as supporting vitamin preparation or can be affiliated with the patients nutrition. Objectives: The purpose of the current model study are to examine biologically significant intermolecular interactions of CYS with N-acetyl-D-glucosamine (NAG) as one of the main component of peptidoglycan of bacterial cell wall and to verify the possibility of noncovalent complexes formation between CYS and ASC molecules using electrospray ionization mass spectrometry (ESI MS) technique. Materials and methods: The objects of the study are model systems composed of CYS and NAG or CYS and ASC prepared in a polar methanol solvent for the ESI MS probing. ESI mass spectra are obtained using the approach earlier developed by us for investigation of the noncovalent complexation of drugs with targeting biomolecules. Results: The experiments reveal that the ESI mass spectrum of (CYS–NAG) model system contains peaks of protonated molecular clusters of CYS with NAG: [CYS•NAG•H]+ and [CYS•2NAG•H]+. Existing of such peaks in the spectrum testifies to formation of stable noncovalent complexes between CYS and NAG in the studied solution. ESI MS examining of (CYS–ASC) system reveals the noncovalent pair complexation of CYS and ASC molecules confirmed by the recording of intensive peak of [CYS•ASC•H]+ cluster in the spectrum. Conclusions: The ESI MS findings point to the possibility of noncovalent complexation of CYS with NAG in the polar media including biological systems. Such complexation between the antibiotic and NAG as component of peptidoglycan of bacterial cell wall is considered to be biologically significant for the process of the cell wall biosynthesis inhibiting by CYS. Stable noncovalent complexes formation between the CYS and ASC molecules is suggested as a potential molecular mechanism of the drugs activity modulation under their joint usage.

The Watson-Crick rare tautomer hypothesis of mutations and reality

Background: In their Nature's seminal work (Nature. 1953;171:737), J.D. Watson and F.H.C. Crick noted that the structure of DNA admits a so-called tautomeric model of spontaneous point mutations. This work reported at the conference "Nanobiophysics-2019" (Kiev) as a plenary report, is actually an attempt to answer the following questions: (i) "Yes, the tautomerism of the bases is a very attractive model, but how important is it in mutagenesis?" by Morgan (Morgan AR. Trends Biochem. Sci. 1993;18:160–163); (ii) What reality does the rare tautomeric mutation model describe? The structure [А×Т]WC was selected in the work. Developing the previously proposed mutation model×of the Watson-Crick pair [А×Т]WC due to the shift of the bases in the pair relative to each other and the interconnection hydrogen bonds (Kryachko ES, Sabin JR. Int. J. Quantum Chem. 2003;91:695–710), it is shown that some resultant structures possess the electron affinity that is 1.7 times higher compared to the canonical pair, which is definitely of interest in the view of the numerous phenomena associated with a charge transfer in and attachment of an electron to DNA. Objectives: Answer the questions raised in the Background, and show the realism of the tautomeric [А×Т]WC-mutation model modified in the present work on the example of the Watson-Crick pair [А×Т]WC that is dubbed as a pair-tautomerism model. Materials and Methods: The key method is a computer simulation based on the density functional method. All calculations performed in the present work use the package of programs GAUSSIAN with the density functional method invoking the Becke-Lee-Yang-Parr density functional, B3LYP. Results: The paper shows the existence and stability of paired tautomeric mutations in a pair of adenine-thymine and investigates to what wobble pairs it can lead. It is also shown that, due to the specific structure of the paired tautomeric mutation of the adenine-thymine pair, the mutation possesses a larger electronic affinity in comparison with the pair that it generates, and thus can be observed in reality and through it one can explain a number of phenomena of charge transfer in DNA, which, again, emphasizes its reality. Conclusions: On the one hand, a generalization of the Watson-Crick tautomeric hypothesis, proposed in this work, specifically for the adenine-thymine pair, the name of the paired tautomeric mutation. This mutation refers to dipole-binding-electron systems, which implies their high adiabatic electron affinity. The latter, on the other hand, emphasizes the realism of the proposed mutational model and its possible application to the explanation of the phenomena of charge transfer in DNA and the processes of attachment electron to DNA.