Organization of the root apical meristem in Linum usitatissimum L. grown at 25°C and 7°C

In the first days of intensive growth of the Linum usitatissimum root, the central part of the apical meristem exhibits usually a 4-tier organization. When growth ceases reorganization of the cell arrangement occurs. It starts by periclinal division of the subprotodermal initials, whose derivatives are forming the secondary columella in the central part of the root cap

Organization of the root apical meristem in Linum usitatissimum L. grown at 25°C and 7°C

In the first days of intensive growth of the Linum usitatissimum root, the central part of the apical meristem exhibits usually a 4-tier organization. When growth ceases reorganization of the cell arrangement occurs. It starts by periclinal division of the subprotodermal initials, whose derivatives are forming the secondary columella in the central part of the root cap

Comparison of air distribution systems in ice rink arena ventilation

The paper presents the requirements and functions of ventilation in ice rink arenas and discusses difficulties and problems of ventilation in such objects. Particular attention has been paid to two types of inside used air distribution systems – traditional-integrated and modern-separated where the functions of tribune ventilation and dehumidification of the air over the ice surface were separated. The flow of humid air and heat in the designed hall was modelled numerically using the ANSYS CFX code based on computational fluid dynamics (CFD) technique. Air distribution systems in the ice rink arena were compared based on the results of numerical calculations

Mercury/Homocysteine Ligation-Induced ON/OFF-Switching of a T–T Mismatch-Based Oligonucleotide Molecular Beacon

A molecular beacon (MB) with stem-loop (hairpin) DNA structure and with attached fluorophore–quencher pair at the ends of the strand has been applied to study the interactions of Hg²⁺ ions with a thymine–thymine (T–T) mismatch in Watson–Crick base-pairs and the ligative disassembly of MB·Hg²⁺ complex by Hg²⁺ sequestration with small biomolecule ligands. In this work, a five base-pair stem with configuration 5′-GGTGG...CCTCC-3′ for self-hybridization of MB has been utilized. In this configuration, the four GC base-pair binding energy is not sufficient to hybridize fully at intermediate temperatures and to form a hairpin MB conformation. The T–T mismatch built-in into the stem area can effectively bind Hg²⁺ ions creating a bridge, T–Hg–T. We have found that the T–Hg–T bridge strongly enhances the ability of MB to hybridize, as evidenced by an unusually large MB melting temperature shift observed on bridge formation, Δ<i><i>T</i></i>_m = +15.1 ± 0.5 °C, for 100 nM MB in MOPS buffer. The observed Δ<i><i>T</i></i>_m is the largest of the Δ<i><i>T</i></i>_m found for other MBs and dsDNA structures. By fitting the parameters of the proposed model of reversible MB interactions to the experimental data, we have determined the T–Hg–T bridge formation constant at 25 °C, <i>K</i>₁ = 8.92 ± 0.42 × 10¹⁷ M^–1 from mercury­(II) titration data and <i>K</i>₁ = 1.04 ± 0.51 × 10¹⁸ M^–1 from the bridge disassembly data; Δ<i>G</i>° = −24.53 ± 0.13 kcal/mol. We have found that the biomarker of oxidative stress and cardiovascular disease, homocysteine (Hcys), can sequester Hg²⁺ ions from the T–Hg–T complex and withdraw Hg²⁺ ions from MB in the form of stable Hg­(Hcys)₂H₂ complexes. Both the model fitting and independent ¹H NMR results on the thymidine–Hg–Hcys system indicate also the high importance of 1:1 complexes. The high value of <i>K</i>₁ for T–Hg–T bridge formation enables analytical determinations of low concentrations of Hg²⁺ (limit of detection LOD = 19 nM or 3.8 ppb, based on 3σ method) and Hcys (LOD = 23 nM, 3σ method). The conditional stability constants for Hg­(Hcys)­H₂²⁺ and Hg­(Hcys)₂H₂ at 52 °C have been determined, β₁₁₂ = 5.37 ± 0.3 × 10⁴⁶ M^–3, β₁₂₂ = 3.80 ± 0.6 × 10⁶⁸ M^–4, respectively

Sensitive electrochemical detection of native and aggregated α-synuclein protein involved in Parkinson's Disease

The aggregation of α-synuclein, a 14 kDa protein, is involved in several human neurodegenerative disorders, including Parkinson´s disease. We studied native and in vitro aggregated α-synuclein by circular dichroism (CD), atomic force microscopy (AFM) and electrochemical methods. We used constant current chronopotentiometric stripping analysis (CPSA) to measure hydrogen evolution catalyzed by α-synuclein (peak H) at hanging mercury drop electrodes (HMDE) and square wave stripping voltammetry (SWSV) to monitor tyrosine oxidation at carbon paste electrodes (CPE). To decrease the volume of the analyte, most of the electrochemical measurements were performed by adsorptive transfer (medium exchange) from 3-6 μL drops of α-synuclein samples. With both CPE and HMDE we observed changes in electrochemical responses of a-synuclein corresponding to protein fibrillization detectable by CD, fluorescence and AFM. Aggregation-induced changes in peak H at HMDE were relatively large in strongly aggregated samples, suggesting that this electrochemical signal may find use in the analysis of early stages of α-synuclein aggregation. This assumption was documented by marked changes in the peak H potential and height in samples withdrawn at the end of the lag and the beginning of the elongation phase. Native α-synuclein can be detected down to subnanomolar concentrations by CPSA

Sensitive Electrochemical Detection of Native and Aggregated x-Synuclein Protein Involved in Parkinson's Disease

The aggregation of α-synuclein, a 14 kDa protein, is involved in several human neurodegenerative disorders, including Parkinson's disease. We studied native and in vitro aggregated α-synuclein by circular dichroism (CD), atomic force microscopy (AFM) and electrochemical methods. We used constant current chronopotentiometric stripping analysis (CPSA) to measure hydrogen evolution catalyzed by α-synuclein (peak H) at hanging mercury drop electrodes (HMDE) and square-wave stripping voltammetry (SWSV) to monitor tyrosine oxidation at carbon paste electrodes (CPE). To decrease the volume of the analyte, most of the electrochemical measurements were performed by adsorptive transfer (medium exchange) from 3-6 L drops of α-synuclein samples. With both CPE and HMDE we observed changes in electrochemical responses of α-synuclein corresponding to protein fibrillization detectable by CD, fluorescence and AFM. Aggregation-induced changes in peak H at HMDE were relatively large in strongly aggregated samples, suggesting that this electrochemical signal may find use in the analysis of early stages of α-synuclein aggregation. This assumption was documented by marked changes in the peak H potential and height in samples withdrawn at the end of the lag and the beginning of the elongation phase. Native α-synuclein can be detected down to subnanomolar concentrations by CPSA

Sensitive electrochemical detection of native and aggregated α-synuclein protein involved in Parkinson's Disease

The aggregation of α-synuclein, a 14 kDa protein, is involved in several human neurodegenerative disorders, including Parkinson´s disease. We studied native and in vitro aggregated α-synuclein by circular dichroism (CD), atomic force microscopy (AFM) and electrochemical methods. We used constant current chronopotentiometric stripping analysis (CPSA) to measure hydrogen evolution catalyzed by α-synuclein (peak H) at hanging mercury drop electrodes (HMDE) and square wave stripping voltammetry (SWSV) to monitor tyrosine oxidation at carbon paste electrodes (CPE). To decrease the volume of the analyte, most of the electrochemical measurements were performed by adsorptive transfer (medium exchange) from 3-6 μL drops of α-synuclein samples. With both CPE and HMDE we observed changes in electrochemical responses of a-synuclein corresponding to protein fibrillization detectable by CD, fluorescence and AFM. Aggregation-induced changes in peak H at HMDE were relatively large in strongly aggregated samples, suggesting that this electrochemical signal may find use in the analysis of early stages of α-synuclein aggregation. This assumption was documented by marked changes in the peak H potential and height in samples withdrawn at the end of the lag and the beginning of the elongation phase. Native α-synuclein can be detected down to subnanomolar concentrations by CPSA