Correlation of TyG-BMI and TyG-WC with severity and short-term outcome in new-onset acute ischemic stroke.

Objectives: To research the connection between the indexes of the indexes of triglyceride-glucose (TyG) combined with obesity indices and the initial neurological severity and short-term outcome of new-onset acute ischemic stroke. Methods: Data of patients with acute ischemic stroke admitted to the Stroke Ward of the Affiliated Hospital of Beihua University from November 2021 to October 2023, were collected. The two indexes were calculated by combining TyG and obesity indices: TyG-body mass index (TyG-BMI) and TyG-waist circumference (TyG-WC). The National Institute of Health Stroke Scale (NIHSS) was used to assess and group patients with neurological deficits within 24 hours of admission: mild stroke (NIHSS ≤5) and moderate-severe stroke (NIHSS >5). Short-term prognosis was evaluated using the modified Rankin Scale (mRS) at discharge or 14 days after onset of the disease and grouped: good outcome (mRS ≤2) and poor outcome (mRS >2). According to the quartiles of TyG-BMI and TyG-WC, the patients were placed into four groups: Q1, Q2, Q3 and Q4. Multi-factor logistic regression analysis was utilized to evaluate the correlation of TyG-BMI and TyG-WC with the severity and short-term outcome. Results: The study included 456 patients. After adjusting for multiple variables, the results showed that compared with the quartile 1, patients in quartile 4 of TyG-BMI had a reduced risk of moderate-severe stroke [Q4: OR: 0.407, 95%CI (0.185-0.894), P = 0.025]; Patients in quartiles 2, 3 and 4 of TyG-BMI had sequentially lower risk of short-term adverse outcomes [Q2: OR: 0.394, 95%CI (0.215-0.722), P = 0.003; Q3: OR: 0.324, 95%CI (0.163-0.642), P = 0.001; Q4: OR: 0.158, 95%CI (0.027-0.349), P <0.001]; Patients in quartiles 3 and 4 of TyG-WC had sequentially lower risk of moderate-severe stroke [Q3: OR: 0.355, 95%CI (0.173-0.728), P = 0.005; Q4: OR: 0.140, 95%CI (0.056-0.351), P <0.001]; Patients in quartiles 3 and 4 of TyG-WC had sequentially lower risk of short-term adverse outcomes [Q3: OR: 0.350, 95%CI (0.175-0.700), P = 0.003; Q4: OR: 0.178, 95%CI (0.071-0.451), P <0.001]. Conclusions: TyG-WC and TyG-BMI were correlated with the severity and short-term outcome of new-onset acute ischemic stroke. As TyG-WC and TyG-BMI increased, stroke severity decreased and short-term outcome was better.

PDE4D single nucleotide polymorphism rs918592 is associated with ischemic Stroke risk in Chinese populations: a meta-analysis.

BACKGROUND: Several studies have investigated the correlation between phosphodiesterase 4D (PDE4D) single nucleotide polymorphism (SNP) rs918592 and the risk of ischemic stroke (IS) in Chinese populations. But the results were inconsistent and inconclusive. Therefore, to resolve this conflict, we conducted a meta-analysis to further elucidate their relationship in Chinese populations. METHODS: Studies focused on SNP rs918592 and IS risk were electronic searched in the databases of PubMed, Embase, ISI Web of Science, Weipu, China National Knowledge Infrastructure (CNKI), Chinese Biomedical (CBM) and Wanfang. The association between SNP rs918592 and IS risk was expressed by odds ratio (OR) with its confidence interval (CI). Begg's and Egger's linear regression tests were used to assess publication bias. The meta-analysis was performed with STATA 11.0 statistical software. Two online prediction websites (HaploReg and RegulomeDB) were adopted to explore the functions of SNP rs918592. RESULTS: The meta-analysis ultimately included 10 studies involving 2,348 cases and 2,289 controls. The results showed that there was a significant correlation between SNP rs918592 and IS risk in Chinese individuals. The G allele had reduced risk of developing IS compared to the A allele (OR 0.83, 95% CI 0.74-0.95, P = 0.005). HaploReg and RegulomeDB analyses suggested that SNP rs918592 and its strongly linked SNPs (e.g. rs34168777) might have regulatory functions. CONCLUSION: This study shows that SNP rs918592 in PDE4D may be a contributor of IS risk in Chinese populations. It offers a good answer for the association of PDE4D SNP rs918592 with IS risk in Chinese populations for the first time.

High level food-grade expression of maltogenic amylase in Bacillus subtilis through dal gene auxotrophic selection marker.

As a food-safe microorganism, Bacillus subtilis has been widely utilized in the production of food enzyme, where a food-grade expression system without antibiotic is required. However, there is no mature system for such expression, since the recombinant plasmid in existing food-grade expression system is unstable especially in high-density fermentation. In this study, we constructed a food-grade expression system based on the dal gene auxotrophic selection marker. Specifically, maltogenic amylase (AmyM) was expressed in dal deletion strain without antibiotic, yielding an activity of 519 U/mL. To increase the expression of AmyM, the promoter of amyM (gene encoding AmyM) was optimized. Furthermore, we found that excessive expression of dal gene was detrimental to the stability of plasmid, and the ribosome binding site (RBS) of dal was mutated with the reduced synthesis of D-alanine. After that, AmyM activity increased to 1364 U/mL with the 100 % stability of plasmid. The 3-L fermentor cultivation was performed with the highest value ever reported in food-grade microorganisms, an activity of 2388 U/mL, showing the scale-up production capability of this system. Besides, it is also able to apply the system for other food enzymes, which indicating the great generalizability of this system for different application.

Preparation and characterization of zein/gelatin electrospun film loaded with ε-polylysine and gallic acid as tuna packaging system.

BACKGROUND: Composite nanofiber films loaded with ε-polylysine (PL) and gallic acid (GA) were prepared using a zein/gelatin (ZG) electrospinning method to develop effective active packaging films for tuna preservation. The morphology, structure, thermal stability, hydrophobicity, antibacterial, and antioxidant properties of the films, and their application for tuna during a period of storage of 4 °C were investigated. RESULTS: PL reduced the average diameter of ZG fibers, whereas GA increased it. The PL/GA/ZG film possessed a well distributed fiber morphology with an average diameter of 810 ± 150 nm. Fourier-transform infrared spectroscopy and X-ray diffraction results showed the physical loading of PL and GA in ZG film with the main chemical bonds and crystal structure unchanged. The addition of both PL and GA reduced hydrophobicity of the ZG film while the PL/GA/ZG film was still hydrophobic. GA enhanced its thermal stability and contributed to its antioxidant activity. PL and GA synergetically enhanced the antibacterial activity of ZG film against Shewanella putrefaciens. PL combined with GA is more suitable for modifying ZG film than GA alone. The PL/GA/ZG film effectively inhibited total viable counts, total volatile base nitrogen, fat oxidation, and texture deterioration of tuna fillets at 4 °C storage, and could extend the shelf life by 3 days. CONCLUSIONS: The PL/GA/ZG nanofiber film demonstrated promising potential for application in the preservation of aquatic products as a new antibacterial and antioxidant food packaging. © 2023 Society of Chemical Industry.

[Research progress on genetic variants of PDE4D and susceptibility to stroke in Chinese population].

The pathogenesis of stroke is complex, with genetic risk factors as one of the main factors. The genetic variants of phosphodiesterase 4D (PDE4D) was significantly associated with the susceptibility to ischemic stroke (IS) in Caucasian population, but its association with the susceptibility to stroke in Chinese population is unclear. This article is intended to review the research on the association between PDE4D genetic variants and stroke susceptibility in Chinese population, aiming to further optimize the relevant research programs and provide reference for the prevention and treatment of stroke in China.

Abundance and characteristics of microplastics in the Wanquan River estuary, Hainan Island.

As the nexus where rivers and oceans meet, estuaries are vulnerable to microplastic (MP) pollution derived from rivers. However, few studies have focused on the pollution status of MPs in small estuarine areas. Here, the abundance and characteristics of MPs in surface water and sediment samples from a small estuary, the Wanquan River estuary, were studied. The average abundance of MPs was 6573 ± 2659 n/m3 in surface water and 1065 ± 696 n/kg dw in sediment samples from the Wanquan River estuary. Most of the MPs in water samples and sediments were red (92.9 % and 88.1 %) fragments (87.4 % and 95.5 %) with sizes <1.0 mm (90.8 % and 92.4 %) made up of antifouling paint particles (APPs) (83.5 % and 89.8 %), respectively. A significant positive correlation (p < 0.01) was found between the concentration of Cu2+ and the abundance of APPs in sediment samples from the Wanquan River estuary. The APPs in the sediments can act as a continuous source of toxic chemicals (e.g., Cu2+) to marine environments. The results of this study expand our knowledge about MP pollution in small estuaries, and the ecological risk of APPs in the Wanquan River estuary to aquatic organisms should not be ignored.

McLeod syndrome with a novel XK frameshift mutation: A case report.

RATIONALE: McLeod syndrome (MLS) is a rare X-linked neurohematologic disorder caused by loss-of-function mutations in the XK gene. However, variations in the XK gene remain to be elucidated. Here, we report the clinical phenotype and genetic features of a patient with MLS caused by a novel frameshift mutation in the XK gene. PATIENT CONCERNS: A 44-year-old man presented with chorea, cognitive impairment, mental disorders, and seizures accompanied by peripheral neuropathy, hyperCKemia, and acanthocytosis. The proband's mother had a mild chorea. One older brother who died 10 years ago without a confirmed diagnosis showed symptoms of both chorea and mental disorders, while the other brother also developed mild chorea. DIAGNOSIS: The patient was diagnosed with MLS based on the family history, clinical manifestations, and accessory examinations. Whole-exome sequencing studies revealed a novel frameshift mutation resulting from a nucleotide variation in exon 2 (452delA) that leads to an amino acid residue conversion from Gln to Arg and early termination of the XK protein (Gln151ArgfsTer2). The patient and one of his older brothers were hemizygotes, and his mother was heterozygous. INTERVENTIONS: The patient was treated with haloperidol to control chorea and levetiracetam to control seizures. OUTCOMES: Six months after treatment, the proband was seizure-free, but showed little improvement in chorea and cognitive dysfunction. LESSON: We describe a family with MLS caused by a novel frameshift mutation in the XK gene. The causes of the mild clinical presentation in the proband's mother require further investigation.

High throughput and very specific screening of anabolic-androgenic steroid adulterants in healthy foods based on stable isotope labelling and flow injection analysis-tandem mass spectrometry with simultaneous monitoring proton adduct ions and chloride adduct ions.

In this work, a stable isotope labelling-flow injection analysis-tandem mass spectrometry (SIL-FIA-MS/MS) with simultaneous monitoring [M+H]+ and [M+Cl]- method was developed for very specific and high throughput screening of anabolic-androgenic steroids (AAS) illegally added to healthy foods. Initially, a simple centrifugation step was carried out for liquid samples, and for solid samples, a solid-liquid extraction step was conducted. Afterwards, batch chemical derivatization was carried out. After adding a certain amount of 13C6-3-NPH labelled AAS standards as the internal standards, it can be directly transferred for FIA-MS/MS analysis based on the no MS response characteristics of 3-NPH. The 3-NPH labelled AAS showed dual-polarity property, observing chloride adduct ion ([M+Cl]-) in negative ion mode and proton adduct ion ([M+H]+) in positive ion mode. The average time cost for pretreatment of each sample was less than 1 min by carrying out batch processing. The subsequent FIA-MS/MS detection enabled rapid and high throughput detection. The addition of 13C6-3-NPH-labelled AAS as internal standards can correct the matrix effect to achieve accurate quantitative analysis. The detection sensitivity was also improved by 2-5 folds after 3-NPH labelling. The limits of detection (LODs) in positive MRM mode were in ranges of 0.1-0.3 ng/mL. The validated method with simultaneous monitoring [M+H]+ and [M+Cl]- was validated in the range of 6.0-1000 ng/mL with the linear coefficient (R2) greater than 0.997. Satisfactory recoveries were found to be in ranges of 93.0-108.7%. The intra-day and inter-day RSDs were in the range of 3.5-9.9% and 5.1-14.1%, respectively. No changes in detection sensitivity of the mass spectrometry and no carry-over effects were found after numerous consecutive injections of AAS derivates. Compared with previously reported methods, the proposed method proved accurate, very specific, high throughput with good sensitivity.

A simultaneous extraction/derivatization strategy coupled with liquid chromatography-tandem mass spectrometry for the determination of free catecholamines in biological fluids.

The current study presents a convenient, rapid and effective simultaneous extraction/derivatization (SEDP) strategy for effective pretreatment of catecholamines (CAs). Commercial zirconium oxide (ZrO2) nanoparticles were employed for the selective capturing of cis-diol containing CAs to remove the biological interferences and phenyl isothiocyanate (PITC) was used for derivatization to improve the ionization and to improve the chromatographic separation. The extraction and derivatization procedures were integrated into one step to simplify the sample pretreatment. Excessive derivatization reagents were removed as well, reducing the degree of contaminations in mass spectrometry. The factors affecting the SEDP process were optimized and the results showed that the detection sensitivity and chromatographic separation of CAs greatly improved compared with underivatized CAs, during LC-MS/MS analysis. Combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), quantifying the concentration of norepinephrine (NE), epinephrine (E) and dopamine (DA) in biological fluids was validated in ranges of 1-200.0 ng/mL with a satisfactory correlation coefficient (R2 > 0.997). The obtained recoveries were in the range of 91.0-109.5% with RSDs less than 9.4%. Finally, significant changes in CAs levels in urine samples of healthy people and pheochromocytoma patients were detected. The developed method offers comparative advantages in terms of sensitivity, specificity and selectivity.

Biochemical Characterization and Mutational Analysis of a Lactone Hydrolase from Phialophora americana.

The mycotoxin zearalenone (ZEN) is a secondary metabolite produced mainly by Fusarium species. ZEN poses health hazards both for humans and animals, as a major contaminant in the food and feed industries. Currently, there is no effective technique for degrading ZEN during industrial processes. In this study, we isolated and biochemically characterized a novel lactone hydrolase, ZHD607, isolated from Phialophora americana, cloned, and exogenously expressed in Pichia pastoris. ZHD607 was characterized as a mesophilic lactone hydrolase having a neutral pH and showing optimal activity at 35 °C and pH 8.0. Two mutants, ZHDM1 and I160Y, generated from ZHD607 based on structure and sequence alignment analyses, exhibited 2.9- and 3.4-fold higher activity towards ZEN than did ZHD607. Molecular dynamics simulation revealed diverse mechanisms driving this improved catalytic activity. These findings enrich our knowledge about ZHD enzyme family and represent an important step toward industrialization of ZEN-detoxifying lactone hydrolases.

Gynurincola endophyticus gen. nov., sp. nov., a novel bacterium of the family Chitinophagaceae.

A Gram-stain-negative, rod-shaped (0.2-0.4 µm×1.2-1.7 µm), endophytic bacterium, designated HBUM179779T, was isolated from the stem of a medicinal plant,Gynura bicolor, collected from Pixian county in Sichuan province, China. The strain did not produce endospores and its cells could secrete mucus. The predominant menaquinone was MK-7. The polar lipids were phosphatidylethanolamine, phosphatidylinositolmannosides, two unknown aminolipids, two unknown glycolipids and an unknown phospholipid. Branched fatty acids (iso-) and hydroxy fatty acids were the main fatty acids, which mainly included iso-C15 : 0, iso-C15 : 1 G and iso-C17 : 0 3-OH. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain HBUM179779T fell within the family Chitinophagaceae, and its closest neighbour was Pseudoflavitalea rhizosphaerae T16R-265T (94.46 %). However, strain HBUM179779T did not make a coherent clade with members of the recognized organisms. The average nucleotide identity value between strain HBUM179779T and Pseudoflavitalea rhizosphaerae T16R-265T was 67.1 %. On the basis of the phylogenetic and phenotypic characteristics of this bacterium, a novel genus and species, Gynurincola endophyticus gen. nov., sp. nov., is proposed. The type strain is HBUM179779T (=CGMCC 1.15525T=NBRC 112424T).

Synergistic effect of acetyl xylan esterase from Talaromyces leycettanus JCM12802 and xylanase from Neocallimastix patriciarum achieved by introducing carbohydrate-binding module-1.

Wheat bran is an effective raw material for preparation xylooligosaccharides; however, current research mainly focuses on alkali extraction and enzymatic hydrolysis methods. Since ester bonds are destroyed during the alkali extraction process, xylanase and arabinofuranosidase are mainly used to hydrolyze xylooligosaccharides. However, alkali extraction costs are very high, and the method also causes pollution. Therefore, this study focuses on elucidating a method to efficiently and directly degrade destarched wheat bran. First, an acidic acetyl xylan esterase (AXE) containing a carbohydrate-binding module-1 (CBM1) domain was cloned from Talaromyces leycettanus JCM12802 and successfully expressed in Pichia pastoris. Characterization showed that the full-length acetyl xylan esterase AXE + CBM1 was similar toe uncovered AXE with an optimum temperature and pH of 55 °C and 6.5, respectively. Testing the acetyl xylan esterase and xylanase derived from Neocallimastix patriciarum in a starch-free wheat bran cooperative experiment revealed that AXE + CBM1 and AXE produced 29% and 16% reducing sugars respectively, compared to when only NPXYN11 was used. In addition, introduced the CBM1 domain into NPXYN11, and the results indicated that the CBM1 domain showed little effect on NPXYN11 properties. Finally, the systematically synergistic effects between acetyl xylan esterase and xylanase with/without the CBM1 domain demonstrated that the combined ratio of AXE + CBM1 coming in first and NPXYN11 + CBM1 s increased reducing sugars by almost 35% with AXE and NPXYN11. Furthermore, each component's proportion remained the same with respect to xylooligosaccharides, with the largest proportion (86%) containing of 49% xylobiose and 37% xylotriose.

The influence of composition on the functionality of hybrid CuO-ZnO-Al2O3/HZSM-5 for the synthesis of DME from CO2 hydrogenation.

A series of CuO-ZnO-Al2O3/HZSM-5 hybrid catalysts with different Cu/Zn ratios and disparate Al2O3 doping were prepared and characterized by XRD, BET, H2-TPR, NH3-TPD and XPS techniques. The optimal Cu/Zn ratio is 7 : 3, and the introduction of a suitable amount of Al2O3 to form hybrid catalysts increased the BET specific area and micropore volume, facilitated the CuO dispersion, decreased the CuO crystallite size, increased the interaction between CuO and ZnO, enhanced the number of weak acid sites, altered the copper chemical state and improved the catalytic performance consequently. The highest CO2 conversion, DME selectivity and DME yield of 27.3%, 67.1% and 18.3%, respectively, were observed over the CZA7H catalyst. The suitable temperature of 260 °C and the appropriate space velocity of 1500 h-1 for one-step synthesis of dimethyl ether (DME) from carbon dioxide (CO2) hydrogenation were also investigated. The 50 h stability of the CZA7H catalyst was also tested.

Co-loading and intestine-specific delivery of multiple antioxidants in pH-responsive microspheres based on TEMPO-oxidized polysaccharides.

In this study, pH-responsive microspheres loaded with multiple antioxidants were developed for intestine-specific delivery and exhibited synergistic activity. They consist of chitosan (CS)-coated microspheres made of TEMPO-oxidized Konjac glucomannan (OKGM) polymers, of which the carboxyl (COO-) groups are cross-linked via ferric ions (Fe3+), allowing the hydrophobic (ß-carotene) and hydrophilic (anthocyanins) antioxidants to be simultaneously incorporated. CLSM images showed successful co-encapsulation of ß-carotene and anthocyanins. The in vitro release kinetics of co-loaded CS-OKGM microspheres in simulated GI fluids indicated that the microspheres retain the dual antioxidants in an acidic gastric environment and release them at intestinal pH. Free radical scavenging experiments demonstrated that multiple antioxidants loaded into OKGM system had synergistic activity with enhanced stability against heat. The multi-functional CS-OKGM microspheres showed great potential for multiple antioxidants and intestine-specific delivery with enhanced stability.

Oral delivery mediated RNA interference of a carboxylesterase gene results in reduced resistance to organophosphorus insecticides in the cotton Aphid, Aphis gossypii Glover.

BACKGROUND: RNA interference (RNAi) is an effective tool to examine the function of individual genes. Carboxylesterases (CarE, EC 3.1.1.1) are known to play significant roles in the metabolism of xenobiotic compounds in many insect species. Previous studies in our laboratory found that CarE expression was up-regulated in Aphis gossypii (Glover) (Hemiptera: Aphididae) adults of both omethoate and malathion resistant strains, indicating the potential involvement of CarE in organophosphorus (OP) insecticide resistance. Functional analysis (RNAi) is therefore warranted to investigate the role of CarE in A. gossypii to OPs resistance. RESULT: CarE expression in omethoate resistant individuals of Aphis gossypii was dramatically suppressed following ingestion of dsRNA-CarE. The highest knockdown efficiency (33%) was observed at 72 h after feeding when dsRNA-CarE concentration was 100 ng/µL. The CarE activities from the CarE knockdown aphids were consistent with the correspondingly significant reduction in CarE expression. The CarE activity in the individuals of control aphids was concentrated in the range of 650-900 mOD/per/min, while in the individuals of dsRNA-CarE-fed aphids, the CarE activity was concentrated in the range of 500-800 mOD/per/min. In vitro inhibition experiments also demonstrated that total CarE activity in the CarE knockdown aphids decreased significantly as compared to control aphids. Bioassay results of aphids fed dsRNA-CarE indicated that suppression of CarE expression increased susceptibility to omethoate in individuals of the resistant aphid strains. CONCLUSION: The results of this study not only suggest that ingestion of dsRNA through artificial diet could be exploited for functional genomic studies in cotton aphids, but also indicate that CarE can be considered as a major target of organophosphorus insecticide (OPs) resistance in A. gossypii. Further, our results suggest that the CarE would be a propitious target for OPs resistant aphid control, and insect-resistant transgenic plants may be obtained through plant RNAi-mediated silencing of insect CarE expression.

Thermochemistry of radicals and molecules relevant to atmospheric chemistry: determination of group additivity values using G3//B3LYP theory.

Thermochemistry of radicals is not as extensively tabulated as that of stable molecular species, even when group additivity schemes are applied. When these radicals contain oxygen or nitrogen atoms, the availability of radical groups is even more limited. Many oxygen- and nitrogen-containing radicals and molecules are present in the atmosphere, and thermochemistry is a valuable component of the development of atmospheric models with predictive capabilities. This paper presents quantum chemical calculations using G3//B3LYP that have been performed to obtain heats of formation, entropies, and heat capacities as a function of the temperature of radicals and molecules from which group additivity values were obtained. Isodesmic and homodesmotic reactions were used to obtain improved estimates of the heats of formation. Thermodynamic property estimates were corrected to account for internal rotations. A total of 323 molecules were studied from which a total of 122 different groups, 21 gauche and cis corrections, and 5 secondary corrections were regressed.

Ab initio study of acrylate polymerization reactions: methyl methacrylate and methyl acrylate propagation.

The kinetic parameters of the free radical propagation of methyl methacrylate and methyl acrylate have been calculated using quantum chemistry and transition state theory. Multiple density functional theory (DFT) methods were used to calculate the activation energy, and it was found that MPWB1K/6-31G(d,p) yields results that are in very good agreement with experimental data. To obtain values of the kinetic parameters that were in the best agreement with experimental data, low frequencies were treated using a one-dimensional internal rotor model. Chain length effects were also explored by examining addition reactions of monomeric, dimeric, and trimeric radicals to monomer for both methyl methacrylate and methyl acrylate. The results show that the values for the addition of the trimeric radical to monomer are closest to experimental data. The kinetic parameters that were calculated using a continuum description of the monomer as a solvent were not significantly different from the vacuum results.

Quantum chemical investigation of low-temperature intramolecular hydrogen transfer reactions of hydrocarbons.

The B3LYP functional was evaluated as a method to calculate reaction barriers and structure-reactivity relationships for intramolecular hydrogen transfer reactions involving peroxy radicals. Nine different basis sets as well as five other MO/DFT and hybrid methods were used in comparing three reactions to available experimental data. It was shown that B3LYP/6-311+G(d,p) offers a good compromise between speed and accuracy for studies in which thermodynamic and kinetic data of many reactions are required. Sixteen reactions were studied to develop structure-reactivity relationships to correlate the activation energy with the heat of reaction. As long as no structural heterogeneities were present in the transition state ring, a simple Evans-Polanyí relationship was shown to capture the activation energy as a function of heat of reaction for reactions in the 1,5-hydrogen shift family. For peroxy radicals undergoing self-abstraction of a hydrogen atom in the 1,5-position, the activation energy was calculated as E(a) (kcal mol(-1)) = 6.3 + Delta H(rxn) (kcal mol(-1)). For reactions with a carbonyl group embedded in the ring of the transition state, the activation energy of peroxy radicals undergoing self-abstraction was correlated as E(a) (kcal mol(-1)) = 18.1 + 0.74 Delta H(rxn) (kcal mol(-1)). The impact of the size of the transition state ring on the activation energy and pre-exponential factor was also probed, and it was shown that these effects can be described using simple nonlinear and linear fits, respectively.