Evaluation Of Kinetic Parameters Research Articles

Evaluation of pyrolysis characteristics and kinetic parameters from several prospected biomass residues by thermogravimetric analysis

Abstract With fossil fuel supplies dwindling and persistent environmental concerns surrounding their consumption, biomass has emerged as a highly promising renewable energy source. Understanding the characteristics of biomass pyrolysis is crucial as it provides valuable insights and guidance for designing and optimizing the pyrolysis process. In this regard, a thermogravimetric assessment was conducted to evaluate the pyrolysis characteristics and kinetic parameters of four prospective biomass sources: Yang Na wood (Dipterocarpus alatus), palmyra palm shell, cotton stalk, and spent coffee grounds with a condition temperature range of 33 °C to 700 °C and a heating rate of 10 °C·min-1 in a nitrogen atmosphere. The kinetic parameters were evaluated using the Coats and Redfern methods, employing various reaction order models. The activation energy and pre-exponential factor were determined for the active pyrolysis stage. The results revealed that the high heating values for all samples ranged from 18.20 to 23.00 MJ·kg-1. Additionally, the onset temperature fell within the range of 243 to 254 °C, while the offset temperature ranged from 365 to 452 °C for all samples. The conversion rate at the offset temperature was 0.67 for Yang Na wood, 0.62 for palmyra palm shell, 0.65 for cotton stalk, and 0.74 for spent coffee grounds. Moreover, the activation energies were measured as 46.47 kJ·mol-1 for Yang Na wood, 52.46 kJ·mol-1 for palmyra palm shell, 64.20 kJ·mol-1 for cotton stalk, and 69.01 kJ·mol-1 for spent coffee grounds. The higher activation energy corresponded to a higher pre-exponential factor. In conclusion, the pyrolysis characteristics and kinetic parameters of the four types of biomasses have been found to be favourable, indicating their potential for promotion and application as a raw material for the pyrolysis process.

Green solvent-based lipid extraction from guava seeds and spent coffee grounds to produce biodiesel: Biomass valorization and esterification/transesterification route

Spent coffee grounds and guava seeds were used as representative biomass residues to analyze the replacement of hexane with alternative green solvents for the extraction of lipids and their application to obtain biodiesel with the aim of contributing to the global zero-waste strategy. Lipid extraction studies were performed with these biomass wastes under different operating conditions. The results showed that the green solvents (i.e., ethyl acetate, ethyl butyrate, and ethyl propionate) outperformed the lipid extraction using hexane, achieving a maximum oil recovery of 24% for guava seed and 16.4% for spent coffee grounds, with ethyl propionate. The impact of solvent-to-biomass ratio, extraction temperature, and biomass particle size on lipid recovery from tested biomass residues was analyzed and discussed. The optimal extraction conditions for both biomasses were ethyl propionate, 0.3 mm of particle size and 40 °C; while the best solvent to biomass ratio were 10 and 8 mL/g for guava seeds and spent coffee grounds, respectively. The lipids extracted with green solvents showed similar physicochemical properties and compositions to those lipids extracted with hexane. Lipid extraction kinetics exhibited an endothermic performance. The kinetic data were suitably described with the first-order model (R2 = 0.92 – 1) with kinetic rate parameters in the range of 0.38–0.59 and 0.28–0.72 min−1, for guava seeds and spent coffee grounds, respectively. The lipids extracted from tested biomass were analyzed as raw source for biodiesel production via transesterification. The best reaction conditions to produce biodiesel (90%) were found at 60 °C, 6 h, 15% of catalyst-to-oil, and molar methanol-to-oil ratio of 26:1 using a one-step process. FAME formation up to 96% was obtained using a two-step esterification/transesterification methodology. A detailed characterization of the biodiesel obtained from the lipid fraction from these biomass wastes was also performed, indicating that transesterification reduced the acid value and viscosity to meet the ASTM standard criteria for biodiesel. The study contributes to the valorization of biomass wastes to produce renewable energy and to minimize the waste management problem.

Thermoluminescence glow curve analysis and kinetic parameters evaluation of different ions co-doped Ca12Al14O33 nanophosphor after γ-irradiation

Thermoluminescence glow curve analysis and kinetic parameters evaluation of different ions co-doped Ca12Al14O33 nanophosphor after γ-irradiation

Modeling of electrocatalytic hydrogen evolution via high voltage alkaline electrolyzer with different nano-electrocatalysts

An energy system based on water for creating hydrogen energy might be less globally restricted than one that uses the available fossil fuels today. Therefore, creating an efficient catalyst and electrolyzer system is necessary to effectively convert renewable energy into chemical energy (hydrogen). In this study, a model based on kinetic reaction rate parameters is proposed for estimating energy efficiency and energy conversion for hydrogen generation in a high-voltage alkaline electrolyzer. Three complementary models, including the thermal, electrochemical, and thermodynamic, are conducted to forecast the thermal time constant, overall thermal resistance, operating temperature, electrolyzer voltage, energy consumption, and energy loss. To ensure that they can operate directly with renewable energy sources, the modeling was expanded to incorporate hydrogen production at a voltage level of 6 V. The model's various parameters were computed using non-linear regression presented in Engineering Equation Solver (EES) utilizing experimental data gathered in a high-voltage alkaline test rig. From their precursors and coated on Ti substrates, nanoparticles of Ag, TiO2, and Ag + TiO2 are created as electrocatalysts for the production of hydrogen. In comparison with the bare Ti electrode, the results revealed that energy efficiencies of the Ag, TiO2, and Ag + TiO2 electrodes have increased by 23%, 28%, and 28%, respectively. The largest improvement in hydrogen energy conversion achieved with TiO2 electrodes over Ti electrodes was 84%. Thermodynamic-thermal models that were integrated showed that the coated electrodes decreased the thermal energy loss (TΔS) and useable energy (ΔG) simultaneously during the electrolysis process. The electrochemical model demonstrated a strong fit to the data from those experiments, indicating that the coated nanomaterials are the most important factor in increasing the electrolyzer energy efficiency-based production of hydrogen. The models presented in this research offered a practical method for increasing hydrogen energy production and energy conversion using nanomaterial to build effective electrolyzer devices. The models described in this study are appropriate for the dynamic simulation of renewable energy-hydrogen systems. As a result, these models are easily connected to economic theories that account for both financial and operation expenses.

Structure and enzymatic characterization of CelD endoglucanase from the anaerobic fungus Piromyces finnis

Anaerobic fungi found in the guts of large herbivores are prolific biomass degraders whose genomes harbor a wealth of carbohydrate-active enzymes (CAZymes), of which only a handful are structurally or biochemically characterized. Here, we report the structure and kinetic rate parameters for a glycoside hydrolase (GH) family 5 subfamily 4 enzyme (CelD) from Piromyces finnis, a modular, cellulosome-incorporated endoglucanase that possesses three GH5 domains followed by two C-terminal fungal dockerin domains (double dockerin). We present the crystal structures of an apo wild-type CelD GH5 catalytic domain and its inactive E154A mutant in complex with cellotriose at 2.5 and 1.8 Å resolution, respectively, finding the CelD GH5 catalytic domain adopts the (β/α)8-barrel fold common to many GH5 enzymes. Structural superimposition of the apo wild-type structure with the E154A mutant-cellotriose complex supports a catalytic mechanism in which the E154 carboxylate side chain acts as an acid/base and E278 acts as a complementary nucleophile. Further analysis of the cellotriose binding pocket highlights a binding groove lined with conserved aromatic amino acids that when docked with larger cellulose oligomers is capable of binding seven glucose units and accommodating branched glucan substrates. Activity analyses confirm P. finnis CelD can hydrolyze mixed linkage glucan and xyloglucan, as well as carboxymethylcellulose (CMC). Measured kinetic parameters show the P. finnis CelD GH5 catalytic domain has CMC endoglucanase activity comparable to other fungal endoglucanases with kcat = 6.0 ± 0.6 s−1 and Km = 7.6 ± 2.1 g/L CMC. Enzyme kinetics were unperturbed by the addition or removal of the native C-terminal dockerin domains as well as the addition of a non-native N-terminal dockerin, suggesting strict modularity among the domains of CelD.Key points• Anaerobic fungi host a wealth of industrially useful enzymes but are understudied.• P. finnis CelD has endoglucanase activity and structure common to GH5_4 enzymes.• CelD’s kinetics do not change with domain fusion, exhibiting high modularity.

Pyrolysis characteristics and kinetic parameters assessment of typical agricultural residues using high heating photothermal TGA

Understanding the complexity of thermal degradation characteristics, kinetic behavior, and thermodynamic parameters is pertinent for the efficient design and process optimization of large-scale conversion systems. Comparative assessment of pyrolysis characteristics and thermodynamic parameters of corn cobs (CC), peanut shells (PS) and sugarcane bagasse (SB) are investigated using high heating rates (100–1000 ℃/min) TGA results. Despite the effect of the heating rate increase on the degradation process of individual samples, increasing heating rates affect pyrolysis characteristics due to compositional differences. With increasing heating rates, the comprehensive pyrolysis index increased sporadically for CC (2.54–44.09 ×104%2/min2 ℃3) and PS (1.36–31.13 ×104%2/min2 ℃3), indicating easier release of volatiles at higher pyrolysis heating rates. The pyrolysis stability index (Rw), which relates to thermal degradation stability, presented an increasing trend (CC>PS>SB) with a heating rate increase (≥106%). Kinetic parameters estimated using model-free methods showed that the activation energies of CC and PS were significantly lower than that of SB. Comparative evaluation of fractional conversions and kinetic parameters using traditional and modified parallel models showed that the double random pore model (DRPM) fitted the best for simulating the experimental results at higher heating rates than other models. The change in Gibbs free energy (ΔG) trend for PS and SB showed a deviation, suggesting reaction difficulties due to higher temperature demands.

Kinetic profiling of novel spirobenzo-oxazinepiperidinone derivatives as equilibrative nucleoside transporter 1 inhibitors

Evaluation of kinetic parameters of drug-target binding, kon, koff, and residence time (RT), in addition to the traditional in vitro parameter of affinity is receiving increasing attention in the early stages of drug discovery. Target binding kinetics emerges as a meaningful concept for the evaluation of a ligand’s duration of action and more generally drug efficacy and safety. We report the biological evaluation of a novel series of spirobenzo-oxazinepiperidinone derivatives as inhibitors of the human equilibrative nucleoside transporter 1 (hENT1, SLC29A1). The compounds were evaluated in radioligand binding experiments, i.e., displacement, competition association, and washout assays, to evaluate their affinity and binding kinetic parameters. We also linked these pharmacological parameters to the compounds’ chemical characteristics, and learned that separate moieties of the molecules governed target affinity and binding kinetics. Among the 29 compounds tested, 28 stood out with high affinity and a long residence time of 87 min. These findings reveal the importance of supplementing affinity data with binding kinetics at transport proteins such as hENT1.

Enzymatic Hydrolysis of Rutin: Evaluation of Kinetic Parameters and Anti-Proliferative, Mutagenic and Anti-Mutagenic Effects.

The bioavailability of glucoside flavonoids is influenced by the nature of the sugar, glucosides being absorbed faster than rhamnoglucosides, for example. One strategy to enhance the bioavailability is enzymatic hydrolysis. In this study, some kinetic parameters of hesperidinase-mediated hydrolysis of rutin were evaluated using an UHPLC/QTOF-MSE analysis of the products of a bioconversion reaction. The resulting hydrolyzed rutins (after 4, 8 and 12 h of reaction) were submitted to anti-proliferative and Cytokinesis-Block Micronucleus (CBMN) assays in CHO-K1 cells. In the hesperidinase-mediated hydrolysis, the final concentration of quercetin-3-O-glucoside (Q3G) was directly proportional to the rutin concentration and inversely proportional to the reaction time. At an anti-proliferative concentration (2.5 μg/mL), hydrolyzed rutin derivatives did not show a mutagenic effect, except for the sample with a higher content of Q3G (after 4 h of the enzymatic hydrolysis of rutin). Moreover, the higher Q3G content in hydrolyzed rutin protected the CHO-K1 cells 92% of the time against methyl methanesulfonate-induced mutagenic damage. These results suggested that the anti-mutagenic effect of hydrolyzed rutin might be related to antioxidant and cell death induction. Presenting a good lipophilicity/hydrophilicity ratio, together with antioxidant and anti-mutagenic activities, the hesperidinase-mediated hydrolyzed rutin seemed to be a promisor raw material for the development of food supplements.

Wearable Sensors and Smart Devices to Monitor Rehabilitation Parameters and Sports Performance: An Overview.

A quantitative evaluation of kinetic parameters, the joint's range of motion, heart rate, and breathing rate, can be employed in sports performance tracking and rehabilitation monitoring following injuries or surgical operations. However, many of the current detection systems are expensive and designed for clinical use, requiring the presence of a physician and medical staff to assist users in the device's positioning and measurements. The goal of wearable sensors is to overcome the limitations of current devices, enabling the acquisition of a user's vital signs directly from the body in an accurate and non-invasive way. In sports activities, wearable sensors allow athletes to monitor performance and body movements objectively, going beyond the coach's subjective evaluation limits. The main goal of this review paper is to provide a comprehensive overview of wearable technologies and sensing systems to detect and monitor the physiological parameters of patients during post-operative rehabilitation and athletes' training, and to present evidence that supports the efficacy of this technology for healthcare applications. First, a classification of the human physiological parameters acquired from the human body by sensors attached to sensitive skin locations or worn as a part of garments is introduced, carrying important feedback on the user's health status. Then, a detailed description of the electromechanical transduction mechanisms allows a comparison of the technologies used in wearable applications to monitor sports and rehabilitation activities. This paves the way for an analysis of wearable technologies, providing a comprehensive comparison of the current state of the art of available sensors and systems. Comparative and statistical analyses are provided to point out useful insights for defining the best technologies and solutions for monitoring body movements. Lastly, the presented review is compared with similar ones reported in the literature to highlight its strengths and novelties.

Evaluation of Kinetic Parameters of Nitrification Process in Biofilter System to Efluent Liquid Waste of Tofu Industry

It is necessary to design a nitrification bioreactor process so that further processing takes place optimally. Performance studies are carried out by evaluating the kinetic parameters that apply specifically to the applied process. The Monod model was applied to determine the value of kinetic parameters in designing and operating a bioreactor. This study aims to determine the value of the kinetic parameters to variations in feed concentration (50, 75, and 100%). The mechanism of the reactor process for the decomposition of pollutants, the influent is fed into the reactor with an up-flow pristaltic pump. The decomposition process provides contact time between organic matter and microorganisms, resulting in a good separation from the reactor outlet. The most optimum kinetic parameter value at 100% wastewater concentration with a value of (k) 1.1086 (dayˉ 1), (Ks) 1.0564 g l-1, (Y) 5.4862 mg MLVSS/mg, (kd) 1.7944 (dayˉ 1), (µm) 6.8372 (dayˉ 1).

Element doping adjusted the built-in electric field at the TiO2/CdS interface to enhance the photocatalytic reduction activity of Cr(VI)

TiO2-based heterojunction photocatalyst is promising for photocatalytic reaction due to its extensive spectral absorption and effective separation of photogenerated carriers. In this study, a simple modification method, element doping (N, I, Fe and Ce) was utilized to modify TiO2/CdS. Results of photocatalytic reduction experiments of Cr(VI) reveal that the photocatalytic activity follows the order of I-TiO2/CdS > Fe-TiO2/CdS > N-TiO2/CdS > TiO2/CdS > Ce-TiO2/CdS, and the kinetic rate parameter values of I-TiO2/CdS is about 29.0 and 2.7 times higher than that of TiO2 and TiO2/CdS, respectively. Meanwhile, the peaks of Ti 2p and Cd 3d exhibit the maximum shift of + 0.51 and –1.18 eV after coupling I-TiO2 with CdS, respectively. DFT calculations and electrochemical test reveal that high-electronegativity I doping can increase the difference of Fermi level between TiO2 and CdS, and I-TiO2/CdS heterostructure presents lower charge migration resistance and higher carrier separation behavior, suggesting that the improvement mechanism of I doping is largely attributed to the enhanced strength of built-in electric field at the interface between TiO2 and CdS. This work presents a simple but effective method to develop heterojunction with high photocatalytic activity via facilitating interface migration of photogenerated carriers.

Evaluation of Oxidative Stability and Kinetic Parameters of the Cottonseed and Soybean Biodiesels by Rancimat and Differential Scanning Calorimetry Techniques

In this study, the oxidative stability of the cottonseed oil biodiesel (CB) and soybean oil biodiesel (SB) was investigated by two methodologies, Rancimat and Differential Scanning Calorimetry (DSC), using samples fresh and aged (mid-term storage condition (100 days)). The biodiesel samples were synthesized by transesterification and characterized by specific mass, kinematic viscosity, acidity value, ester content, viscosity index, and peroxide value. The activation energy (<em>E<sub>a</sub></em>), Arrhenius pre-exponential factor (<em>Z</em>), reaction order (<em>n</em>), and reaction rate at constant temperature (<em>k</em>(T)) were calculated by Borchardt and Daniels method. The results showed that oxidation affected the physicochemical properties of the biodiesel samples, especially, acidity (mg KOH/g), peroxide value (meq/1000 g), and induction period, with a decrease of around 55% for CB and 29% for SB. For kinetic parameters, the k(T) of both aged samples presented the highest values, with an increase of around 314% for SB. It was also observed that the rate constants increased with decreasing values of the induction period, in agreement with the current literature. According to the evaluation, the Borchardt and Daniels method can be recommended for a quick assessment of the biodiesel oxidation kinetic parameters.

Biodiesel synthesized from the blend of Thai red and Elaeis guineensis oil: An application of calcined base, optimization, kinetics, and thermodynamic parameters studies

The study emphasized the use of the mixed oil (MO) extracted from Elaeis guineensis and Thai Red oilseeds for the synthesis of biodiesel using a derived bio-base catalyst from calcined Littorina littorea shell powder. The MO properties were determined with a view to examine its quality for biodiesel production. The derived calcined catalyst was characterized using scanning electron microscopy (SEM), X-ray fluorescence (XRF), Fourier transforms infrared spectroscopy (FTIR), BET adsorption analysis, and Hammett indicator. Process optimization of biodiesel synthesized was carried out by considering four constraint variables: reaction time (60–80 min), catalyst conc. (2–6% wt.), reaction temp.(55–75 °C), and ethanol/oil molar ratio (E-OH/OMR) (4–8 vol./vol.) using design expert STAT EASE 360. For the rate of reaction, degree of disorderliness, and the activation energy of the transesterification process, kinetics and thermodynamic parameters were considered using Eyring Polanyi and Gibb's Duhem equations, while the qualities of biodiesel as well as its economic appraisal were also carried out. Results obtained showed the API gravity ratio of the mixed oil of 2:3, which indicated a perfect blend ratio. Statistical analysis validation via response surface methodology indicated a biodiesel yield of 98.90% (wt./wt.) was obtained at 69.83 (min), 5.86% (wt.), 68.17 °C, and 7.04 (vol./vol.). Kinetic parameter evaluation showed the activation energy (Ea) of transesterification of the mixed oil to biodiesel to be 55.44 kJ mol−1 while thermodynamic parameters (Gibb's free-ΔGθ) were obtained as follows: 184.87 kJ mol−1, 179.77 kJ mol−1, and 174.67 kJ mol−1, at enthalpy (ΔHθ) value of 53.38 kJ mol−1 and entropy (ΔSθ) of -509.64 J mol−1, respectively. Catalyst reusability test was altered at 7th cycles, while the qualities of biodiesel were found comparable with biodiesel recommended standards (ASTM D6751 and EN 14214).

Reaction kinetics for high pressure hydrogen oxy-combustion in the presence of high levels of H2O and CO2

Novel shock tube experimental ignition delay time (IDT) data are provided to delineate the impact of high concentrations (45% by mole) of H2O and CO2 on IDTs of stoichiometric 4% H2. Ignition delay experiments were conducted using a high- and a low-pressure shock tube facility. High-pressure experiments were performed at pressures of 37-43.8 bar and temperatures of 1084-1242 K in four different bath gases, namely: Ar, 45%H2O/Ar, 30%H2O/15%CO2/Ar, and 45%CO2/Ar. Low-pressure experiments were conducted at 2.1-2.7 bar and 926-1198 K in Ar and 45%CO2/Ar bath gases. Impacts of non-ideal ignition phenomena that may occur in the presence of large amounts of H2O and CO2 were also analyzed. A minimally-tuned H2/CO reaction mechanism, CanMECH 1.0, targeting high-pressure combustion in the presence of large concentrations of H2O and CO2 is presented. The mechanism is constructed from unadjusted kinetic rate parameters from theoretical / experimental elementary reaction rate determinations. The only adjusted rate in CanMECH 1.0 is the much disputed Ar-specific low-pressure-limit pre-exponential factor of H + O2 (+Ar) = HO2 (+Ar) within the uncertainty bounds of the source rate. Validity of CanMECH 1.0 is confirmed against shock tube IDT data of this work, as well as selected H2 and H2/CO shock tube IDT datasets from literature. The performance of the model is compared to Keromnes et al. model (Combust. Flame 160 (2013) 995-1011). CanMECH 1.0 outperformed Keromnes et al. for 16 datasets out of 26 and exhibited a similar performance for another two. In particular, CanMECH 1.0 outperformed Keromnes et al. in predicting shock tube IDTs for H2O- and CO2-laden reactive mixtures, as well as all IDT data at pressures of 17-43.8 bar, which are of distinct value to pressurized oxy-fuel combustion applications relevant to this work.

Evaluation of the Sublimation Process of Some Purine Derivatives: Sublimation Rate, Activation Energy, Mass Transfer Coefficients and Phenomenological Models.

Caffeine and theophylline are compounds with important applications in the pharmaceutical industry and other fields of the chemical industry. These purine derivatives have simple chemical structures, therefore, the evaluation of their sublimation process contributes to the development of mass transfer analysis methods that can later be applied to other compounds with more complex structures. With the help of thermogravimetric analysis in isothermal conditions, the kinetic study of the sublimation of caffeine and theophylline, along with the evaluation of kinetic parameters (activation energy and the pre-exponential factor), was carried out. Global mass transfer coefficients were determined, which vary for caffeine between 53 × 10−8 and 631 × 10−8 mol/s·m2·Pa, and for theophylline between 68 × 10−8 and 441 × 10−8 mol/s·m2·Pa. The dimensionless equations of the form: have been proposed, which allow the determination of individual mass transfer coefficients at temperatures between 130 and 160 °C for caffeine and between 170 and 200 °C for theophylline.

Evaluation of tracer kinetic parameters in cervical cancer using dynamic contrast-enhanced MRI as biomarkers in terms of biological relevance, diagnostic performance and inter-center variability.

This study assessed the clinical value of parameters derived from dynamic contrast-enhanced (DCE) MRI with respect to correlation with angiogenesis and proliferation of cervical cancer, performance of diagnosis and reproducibility of DCE-MRI parameters across MRI scanners. A total of 113 patients with cervical carcinoma from two centers were included in this retrospective study. The DCE data were centralized and processed using five tracer kinetic models (TKMs) (Tofts, Ex-Tofts, ATH, SC, and DP), yielding the following parameters: volume transfer constant (Ktrans), extravascular extracellular volume (Ve), fractional volume of vascular space (Vp), blood flow (Fp), and permeability surface area product (PS). CD34 counts and Ki-67 PI (proliferation index) of cervical cancer and normal cervix tissue were obtained using immunohistochemical staining in Center 1. CD34 count and Ki-67 PI in cervical cancer were significantly higher than in normal cervix tissue (p<0.05). Parameter Ve from each TKM was significantly smaller in cervical cancer tissue than in normal cervix tissue (p<0.05), indicating the higher proliferation of cervical cancer cells. Ve of each TKM attained the largest AUC to diagnose cervical cancer. The distributions of DCE parameters for both cervical cancer and normal cervix tissue were not significantly different between two centers (P>0.05). Parameter Ve was similar to the expression of Ki-67 in revealing the proliferation of tissue cells, attained good performance in diagnosis of cervical cancer, and demonstrated consistent findings on measured values across centers.

Uncertainty Quantification of Michaelis–Menten Kinetic Rates and Its Application to the Analysis of CRISPR‐Based Diagnostics

AbstractMichaelis–Menten kinetics is an essential model to rationalize enzyme reactions. The quantification of Michaelis–Menten parameters can be very challenging as it is sensitive to even small experimental errors. We here present a quantification of the uncertainty inherent to the experimental determination of kinetic rate parameters for enzymatic reactions. We study the influence of several sources of uncertainty and bias, including the inner filter effect, pipetting errors, number of points in the Michaelis–Menten curve, and flat‐field correction. Using Monte Carlo simulations and analyses of experimental data, we compute typical uncertainties of , , and catalytic efficiency . As a salient example, we analyze the extraction of such parameters for CRISPR‐Cas systems. CRISPR diagnostics have recently attracted much interest and yet reports of these enzymatic kinetic rates have been highly unreliable and inconsistent.

Uncertainty Quantification of Michaelis-Menten Kinetic Rates and Its Application to the Analysis of CRISPR-Based Diagnostics.

Michaelis-Menten kinetics is an essential model to rationalize enzyme reactions. The quantification of Michaelis-Menten parameters can be very challenging as it is sensitive to even small experimental errors. We here present a quantification of the uncertainty inherent to the experimental determination of kinetic rate parameters for enzymatic reactions. We study the influence of several sources of uncertainty and bias, including the inner filter effect, pipetting errors, number of points in the Michaelis-Menten curve, and flat-field correction. Using Monte Carlo simulations and analyses of experimental data, we compute typical uncertainties of , , and catalytic efficiency . As a salient example, we analyze the extraction of such parameters for CRISPR-Cas systems. CRISPR diagnostics have recently attracted much interest and yet reports of these enzymatic kinetic rates have been highly unreliable and inconsistent.

Enzyme Kinetics and Detector Sensitivity Determine Limits of Detection of Amplification-Free CRISPR-Cas12 and CRISPR-Cas13 Diagnostics.

Interest in CRISPR-Cas12 and CRISPR-Cas13 detection continues to increase as these detection schemes enable the specific recognition of nucleic acids. The fundamental sensitivity limits of these schemes (and their applicability in amplification-free assays) are governed by kinetic rates. However, these kinetic rates remain poorly understood, and their reporting has been inconsistent. We quantify kinetic parameters for several enzymes (LbCas12a, AsCas12a, AapCas12b, LwaCas13a, and LbuCas13a) and their corresponding limits of detection (LoD). Collectively, we present quantification of enzyme kinetics for 14 guide RNAs (gRNAs) and nucleic acid targets for a total of 50 sets of kinetic rate parameters and 25 LoDs. We validate the self-consistency of our measurements by comparing trends and limiting behaviors with a Michaelis-Menten trans-cleavage reaction kinetics model. For our assay conditions, activated Cas12 and Cas13 enzymes exhibit trans-cleavage catalytic efficiencies between order 105 and 106 M-1 s-1. For assays that use fluorescent reporter molecules (ssDNA and ssRNA) for target detection, the kinetic rates at the current assay conditions result in an amplification-free LoD in the picomolar range. The results suggest that successful detection of target requires cleavage (by an activated CRISPR enzyme) of the order of at least 0.1% of the fluorescent reporter molecules. This fraction of reporters cleaved is required to differentiate the signal from the background, and we hypothesize that this required fraction is largely independent of the detection method (e.g., endpoint vs reaction velocity) and detector sensitivity. Our results demonstrate the fundamental nature by which kinetic rates and background signal limit LoDs and thus highlight areas of improvement for the emerging field of CRISPR diagnostics.

Deep hydrodesulfurization of gas oils with high sulfur content: Experiment and kinetic modeling

The hydrodesulfurization of straight-run gas oils (SRGO-HS) with high content of sulfur (about 2 wt%) and its mixture with light coker gas oil (CGO) has been studied over CoMo/Al2O3 catalyst using a trickle bed down-flow reactor at the 335–365 °C, H2/HC − 300 Nm3/m3, LHSV − 0.8–2.5 h−1 and 3.5–5.1 MPa. The possibility of ultra-low sulfur diesel (<10 ppmS) production using feedstocks with sulfur content exceeding 2 wt% was demonstrated under conditions simulating industrial one. To predict the effect of process parameters on the amount of sulfur in products four kinetic models with different insight into the reactivity of individual S-containing compounds were considered. The first model is simplified kinetics based on power law rate equations, taking into account overall sulfur content, the second group includes LHHW type rate equations. The models 3 and 4 take into consideration the difference in the reactivity of sulfur-containing components. Model 3 classifies the total sulfur into two subgroups Se (easy reactive compounds) and Sr (refractory sulfur compounds - dibenzothiophene and its derivatives). In Model 4 the group Sr is divided into three more subgroups. Kinetic rate parameters i.e. frequency factors, apparent activation energies, and adsorption enthalpies, were estimated by fitting the experimental data obtained using the SRGO-HS/CGO feedstock to the models. All kinetic models predicted the experimentally determined conversions of sulfur with a relatively good accuracy (±20%). The kinetic models were verified by comparing the simulation results with the experimental data obtained using the other oil fractions (SRGO-LS) with lower content of sulfur (1.05 wt%). A better agreement was observed between the experiments and prediction by models 3 and 4.