Predicting abrupt depletion of dissolved oxygen in Chaohu lake using CNN-BiLSTM with improved attention mechanism.

Depletion of dissolved oxygen (DO) is a significant incentive for biological catastrophic events in freshwater lakes. Although predicting the DO concentrations in lakes with high-frequency real-time data to prevent hypoxic events is effective, few related experimental studies were made. In this study, a short-term predicting model was developed for DO concentrations in three problematic areas in China's Chaohu Lake. To predict the DO concentrations at these representative sites, which coincide with biological abnormal death areas, water quality indicators at the three sampling sites and hydrometeorological features were adopted as input variables. The monitoring data were collected every 4 h between 2020 and 2023 and applied separately to train and test the model at a ratio of 8:2. A new AC-BiLSTM coupling model of the convolution neural network (CNN) and the bidirectional long short-term memory (BiLSTM) with the attention mechanism (AM) was proposed to tackle characteristics of discontinuous dynamic change of DO concentrations in long time series. Compared with the BiLSTM and CNN-BiLSTM models, the AC-BiLSTM showed better performance in the evaluation criteria of MSE, MAE, and R2 and a stronger ability to capture global dependency relationships. Although the prediction accuracy of hypoxic events was slightly worse, the general time series characteristics of abrupt DO depletion were captured. Water temperature regularly affects DO concentrations due to its periodic variations. The high correlation and the universal importance of total nitrogen (TN) and total phosphorus (TP) with DO reveals that point source pollution are critical cause of DO depletion in the freshwater lake. The importance of NTU at the Zhong Miao Station indicates the self-purification capacity of the lake is affected by the flow rate changes brought by the tributaries. Calculating linear correlations of variables in conjunction with a permutation variable importance analysis enhanced the interpretability of the proposed model results. This study demonstrates that the AC-BiLSTM model can complete the task of short-term prediction of DO concentration of lakes and reveal its response features of timing and magnitude of abrupt DO depletion.

Change in self-image pressure level before and after autologous fat breast augmentation and its effect on social adaptability.

BACKGROUND: There is an increasingly strong demand for appearance and physical beauty in social life, marriage, and other aspects with the development of society and the improvement of material living standards. An increasing number of people have improved their appearance and physical shape through aesthetic plastic surgery. The female breast plays a significant role in physical beauty, and droopy or atrophied breasts can frequently lead to psychological inferiority and lack of confidence in women. This, in turn, can affect their mental health and quality of life. AIM: To analyze preoperative and postoperative self-image pressure-level changes of autologous fat breast augmentation patients and their impact on social adaptability. METHODS: We selected 160 patients who underwent autologous fat breast augmentation at the First Affiliated Hospital of Xinxiang Medical University from January 2020 to December 2022 using random sampling method. The general information, self-image pressure level, and social adaptability of the patients were investigated using a basic information survey, body image self-assessment scale, and social adaptability scale. The self-image pressure-level changes and their effects on the social adaptability of patients before and after autologous fat breast augmentation were analyzed. RESULTS: We collected 142 valid questionnaires. The single-factor analysis results showed no statistically significant difference in the self-image pressure level and social adaptability score of patients with different ages, marital status, and monthly income. However, there were significant differences in social adaptability among patients with different education levels and employment statuses. The correlation analysis results revealed a significant correlation between the self-image pressure level and social adaptability score before and after surgery. Multiple factors analysis results showed that the degree of concern caused by appearance in self-image pressure, the degree of possible behavioral intervention, the related distress caused by body image, and the influence of body image on social life influenced the social adaptability of autologous fat breast augmentation patients. CONCLUSION: The self-image pressure on autologous fat breast augmentation patients is inversely proportional to their social adaptability.

[Research Advances of Groundwater Nitrate Pollution and Source Apportionment in China].

Groundwater nitrate (NO3-) contamination in China has become a serious environmental problem, especially in agricultural production areas, which greatly affects the safety of drinking groundwater and requires urgent attention. In this study, the main sources of groundwater nitrate in China were reviewed, including atmospheric deposition, soil nitrogen, agricultural fertilization, and fecal sewage, among which fecal sewage and agricultural fertilization were the main reasons for the excessive groundwater nitrate. The application of hydrochemical analysis, multivariate statistical analysis, stable isotope tracer method, and microbial source tracking in the source apportionment of groundwater nitrate was summarized. All types of source apportionment methods had certain limitations. It is suggested that a variety of methods should be used to identify the source of groundwater nitrate, and the contribution rate of different pollution sources should be calculated using multivariate statistical analysis and isotope quantitative analysis models. The source apportionment of nitrate pollution has undergone a process from qualitative to quantitative research. At present, the SIAR and MixSIAR models based on δ15N-NO3-and δ18O-NO3- have been used widely to analyze the source of nitrate. However, due to the overlap of isotope characteristic values of different input end-members, the difference in δ15N-NO3-and δ18O-NO3- values under different spatial and temporal changes, and the influence of isotope fractionation in the process of nitrogen migration and transformation, the results calculated by the model remain uncertain. It is necessary to further optimize the analytical method of the model to obtain the source of nitrate pollution and its contribution rate more accurately to further aid in the scientific management of groundwater resources.

[Hydrochemical Characteristics and Control Factors of Surface Water in Kuaize River Basin at the Upper Pearl River].

The Kuaize River is a small typical karst watershed in the source area of the Pearl River as well as an important coal mining area in Eastern Yunnan with a fragile ecological environment. Strengthening the research on the water environment in the region plays an important role in supporting the comprehensive management of the ecological environment and water resources in the source region of the Pearl River. Through the systematic collection of surface water, karst groundwater, and mine water samples, mathematical statistics analysis, correlation analysis, ion ratio analysis, absolute principal component scores multiple linear regression(APCS-MLR), and other methods were used to study the characteristics of hydrochemical evolution and control factors in Kuaize River Basin. The results showed that the average pH value of surface water in Kuaize River Basin was 7.8, which was weakly alkaline. The main cations were Ca2+ and Na+, showing the characteristics of Ca2+>Na+>Mg2+>K+. The main anions were HCO3- and SO42-, showing the characteristics of HCO3->SO42->NO3->Cl-. The variation coefficients of Na+, SO42-, and NO3- in surface water were high, showing strong spatial variability. The water chemical type of the trunk stream was mainly HCO3-Ca, whereas the water chemical type of the tributary was relatively complex, mainly HCO3-Ca, HCO3-Ca·Na, and HCO3·SO4-Ca·Na. The chemical composition of surface water was mainly affected by rock weathering, cation exchange, and human activities. Ca2+, Mg2+, Na+, and HCO3- in surface water mainly came from the weathering of carbonate rock and silicate rock; SO42- mainly came from the oxidation of sulfide, such as pyrite in coal seams; K+, Cl-, and NO3- mainly came from domestic sewage and agricultural activities. The APCS-MLR receptor model analysis results showed that the surface water in the Kuaize River Basin was mainly affected by sulfide oxidation, carbonate weathering, weathering of silicate rock in mine water, domestic sewage, agricultural activities, and unknown sources. In general, the contribution rate of human activities such as mining, domestic sewage, and agricultural activities to the surface water reached 47.17%, indicating that human activities were the key driving factor of surface water chemistry in the Kuaize River Basin.

Direct arene trifluoromethylation enabled by promiscuous activity of fungal laccase.

Laccase from Trametes versicolor was found to oxidize non-phenolic arenes and enable the trifluoromethylation of arenes in the presence of in situ generated CF3 radicals at a catalyst loading as low as 0.0034%. The biocatalytic trifluoromethylation proceeded under mild conditions and could increase the yield by up to 12 fold, compared to the control.

Clinical Effects of Pulsed Dye Laser Dynamically Combined with Triamcinolone Acetonide in the Treatment of Postoperative Recurrence Keloids.

Purpose: This study aimed to explore the clinical effects of pulsed dye laser (PDL) dynamically combined with triamcinolone acetonide (TAC) in the treatment of post-operative keloids recurrence. Materials and Methods: This study retrospectively analysed the clinical data of 29 keloid patients (with 39 keloids) from April 2014 to February 2020. The patients were divided into TAC group (14 patients with 19 keloids) and dynamic treatment group (15 patients with 20 keloids) according to the post-operative treatment that they received. The keloids were assessed by Vancouver scar scale (VSS), patient and observer scar assessment scale (POSAS) and the effect of keloids on the quality of life of patients was evaluated with dermatology life quality index (DLQI) scale before the surgical treatment, at any time of relapse, and 24 months after the surgical treatment. The recurrence-free interval, relative cure time, and the cumulative times of TAC injection when the relative cure could be assessed as achieved, and the incidence of adverse reactions were calculated. Results: Patients experiencing a recurrence within 2 years after surgery included 19 keloids (25.33%) that developed a recurrent event within 6 months, 34 keloids (45.33%) that within 12 months, and 39 keloids (52.00%) that within 24 months after surgery. Anterior chest keloid had the highest recurrence rate and ear keloid had the lowest recurrence rate. The total pigmentation and vascularity (VSS and POSAS) scores of patients' keloids in TAC group and dynamic treatment group 24 months after treatment were significantly lower than those before treatment and at relapse (P < 0.05), the total VSS and POSAS scores were significantly lower at 24 months than before treatment and at relapse (P < 0.05), and the DLQI scale score was significantly lower at 24 months than before treatment (P < 0.05). The VSS and POSAS scores of patients' keloids at 24 months after treatment were significantly lower in the dynamic treatment group than in the TAC group. The relative cure time of patients' keloids in the dynamic treatment group was 6.47 ± 2.72 months, which was significantly shorter than 8.65 ± 3.67 months in the TAC group (P < 0.05). The cumulative number of TAC injections that were given to achieve a relative cure of patients' keloids in dynamic treatment group was 3.60 ± 1.76, which was significantly less than 5.24 ± 2.25 in TAC group. The total incidence of adverse reactions was lower in the dynamic group than in TAC group, but this difference did not reach statistical significance (P > 0.05). Conclusions: Compared with TAC injection alone, PDL dynamically combined with TAC in the treatment of keloid with post-operative recurrence can shorten the relative cure time, reduce the number of TAC injections and improve the clinical efficacy.

[Hydrochemical Characteristics and Controlling Factors in Wudu River Basin of Guizhou Province].

TheWudu River is a typical mining-type watershed in the karst mountainous area of western Guizhou Province. Based on the collection of the main stream, tributaries, spring water, and mine water samples in Wudu River Basin, the hydrochemical characteristics and control factors of Wudu River Basin were studied using Gibbs diagram, Piper diagram, and mathematical statistics analysis, and the solute contribution rate of different sources was calculated. The results revealed that the pH value of the water in the Wudu River Basin ranged from 7.87 to 8.52, with an average of 8.14. The TDS values ranged from 135 to 243 mg·L-1, with an average of 191.7 mg·L-1. The major cations in natural river and spring water were Ca2+ and Mg2+, the major anion was HCO3-, and the hydrochemical type was HCO3-Ca. However, owing to the influence of mining activities, the major cations in some tributaries were Ca2+ and Na+, and the hydrochemical types transitioned to HCO3·SO4-Ca and HCO3·SO4-Ca·Na. The ion components of river water in Wudu River Basin were affected by mine water discharge and cation exchange, carbonate rock weathering, silicate rock weathering, and agricultural fertilization. The high concentration of SO42- and Na+in mine water was the primary source of SO42- and Na+in the tributaries of the Wudu River. The method for calculating chemical material balance showed that the contribution rate of carbonate rock weathering ranged from 44.12% to 86.92%, with an average of 74.32%. The contribution rate of mining activities ranged from 3.28% to 37.07%, with an average of 11.61%. Carbonate rock weathering was the main controlling factor of hydrochemical components in the Wudu River Basin; meanwhile, mining activities also had a certain impact on river water chemistry but they showed spatial heterogeneity. The average contribution rates of atmospheric precipitation, silicate rock weathering, agricultural activities, and domestic sewage were 3.75%, 4.67%, 2.85%, and 2.81%, respectively, which had a limited impact on the hydrochemical components of the basin.

Interpersonal Competition in Elderly Couples: A Functional Near-Infrared Spectroscopy Hyperscanning Study.

Elderly people tend not to compete with others, and if they do, the mechanism behind the competition is not clear. In this study, groups of elderly couples and matched cross-sex controls were recruited to perform a competitive button-pressing task, while their brain signals were simultaneously collected using functional near-infrared spectroscopy (fNIRS) hyperscanning. Several fundamental observations were made. First, controls showed attenuated interpersonal competition across task processes, but couples held the competition with each other. Second, couples demonstrated increased inter-brain synchronization (IBS) between the middle temporal cortex and the temporoparietal junction across task processes. Third, Granger causality analysis in couples revealed significant differences between the directions (i.e., from men to women, and from women to men) in the first half of the competitive task, whereas there was no significant difference in the second half. Finally, the groups of couples and controls could be successfully discriminated against based on IBS by using a machine-learning approach. In sum, these findings indicate that elderly couples can maintain interpersonal competition, and such maintenance might be associated with changes in the IBS of the mentalizing system. It suggests the possible positive impact of long-term spouse relationships on interpersonal interactions, both behaviorally and neurally, in terms of competition.

Assembly and Evolution of Artificial Metalloenzymes within E. coli Nissle 1917 for Enantioselective and Site-Selective Functionalization of C─H and C═C Bonds.

The potential applications afforded by the generation and reactivity of artificial metalloenzymes (ArMs) in microorganisms are vast. We show that a non-pathogenic E. coli strain, Nissle 1917 (EcN), is a suitable host for the creation of ArMs from cytochrome P450s and artificial heme cofactors. An outer-membrane receptor in EcN transports an iridium porphyrin into the cell, and the Ir-CYP119 (CYP119 containing iridium porphyrin) assembled in vivo catalyzes carbene insertions into benzylic C-H bonds enantioselectively and site-selectively. The application of EcN as a whole-cell screening platform eliminates the need for laborious processing procedures, drastically increases the ease and throughput of screening, and accelerates the development of Ir-CYP119 with improved catalytic properties. Studies to identify the transport machinery suggest that a transporter different from the previously assumed ChuA receptor serves to usher the iridium porphyrin into the cytoplasm.

Directed Evolution of Artificial Metalloenzymes in Whole Cells.

Artificial metalloenzymes (ArMs), created by introducing synthetic cofactors into protein scaffolds, are an emerging class of catalyst for non-natural reactions. Although many classes of ArMs are known, in vitro reconstitution of cofactors and proteins has been a limiting step in the high-throughput screening and directed evolution of ArMs because purification of individual host proteins is time-consuming. We describe the application of a platform to combine mutants of the P450 enzyme CYP119 and the cofactor Ir(Me)MPIX in vivo, by coexpression of the CYP119 mutants with the heme transporter encoded by the hug operon, to the directed evolution of ArMs containing Ir(Me)MPIX in whole cells. We applied this platform to the development an ArMs catalyzing the insertion of the acyclic carbene from α-diazopropanoate esters (Me-EDA) into the N-H bonds of N-alkyl anilines, a combination of carbene and amine classes for which mutant enzymes of natural hemoproteins previously reacted with low enantioselectivity. The mutants of the artificial metalloenzyme Ir(Me)CYP119 identified by an evolution campaign involving more than 4000 mutants are shown to catalyze the reaction of Me-EDA with N-methyl anilines to form chiral chiral amino esters with high TON and good enantioselectivity, thereby demonstrating that the directed evolution of ArMs can rival that of natural enzymes in vivo.

Unnatural biosynthesis by an engineered microorganism with heterologously expressed natural enzymes and an artificial metalloenzyme.

Synthetic biology enables microbial hosts to produce complex molecules from organisms that are rare or difficult to cultivate, but the structures of these molecules are limited to those formed by reactions of natural enzymes. The integration of artificial metalloenzymes (ArMs) that catalyse unnatural reactions into metabolic networks could broaden the cache of molecules produced biosynthetically. Here we report an engineered microbial cell expressing a heterologous biosynthetic pathway, containing both natural enzymes and ArMs, that produces an unnatural product with high diastereoselectivity. We engineered Escherichia coli with a heterologous terpene biosynthetic pathway and an ArM containing an iridium-porphyrin complex that was transported into the cell with a heterologous transport system. We improved the diastereoselectivity and product titre of the unnatural product by evolving the ArM and selecting the appropriate gene induction and cultivation conditions. This work shows that synthetic biology and synthetic chemistry can produce, by combining natural and artificial enzymes in whole cells, molecules that were previously inaccessible to nature.

Downregulation of CYP2E1 is associated with poor prognosis and tumor progression of gliomas.

OBJECTIVE: To explore the role and possible regulatory mechanisms of CYP2E1 in gliomas. METHODS: RNA-seq data and corresponding clinical information of glioma patients were collected from The Cancer Genome Atlas and Chinese Glioma Genome Atlas, and mRNA data of normal brain tissues were obtained by the Genotype-Tissue Expression project. The Wilcoxon test was performed to analyze the correlation between CYP2E1 expression and glioma subtypes. Univariate and multivariate Cox proportional hazards regression, receiver operating characteristic curves, and Kaplan-Meier plots were used to evaluate the prognostic value of CYP2E1 in glioma. Functional enrichment analyses and immune infiltration analyses were performed to investigate the potential function of CYP2E1 in gliomas. Moreover, we investigated the miRNA and epigenetic mechanisms that regulate CYP2E1 expression. Finally, network pharmacology and molecular docking experiments were used to predict drugs that target CYP2E1. RESULTS: The downregulation of CYP2E1 expression may predict a poor prognosis for glioma patients. CYP2E1 expression decreased with increasing WHO grade (II-IV), and its level was correlated with clinical features, including age, 1p19q codeletion status, and IDH state in glioma tissues. Furthermore, CYP2E1 was involved in lipid metabolism and ferroptosis and related to the tumor immune microenvironment due to its strong correlation with the levels of infiltrating monocytes and Tregs. Moreover, variation in the total methylation level and copy number of CYP2E1 was moderately correlated with its mRNA expression (p < 0.05). CYP2E1 was predicted to be targeted by hsa-miR-527, whose expression was negatively related to CYP2E1 mRNA expression (p < 0.05). In addition, effective compounds that target CYP2E1, including 18beta-glycyrrhetinic acid, styrene, toluene, nicotine, m-xylene, p-xylene, and colchicine, were identified. CONCLUSION: The downregulation of CYP2E1, which affects lipid metabolism and the ferroptosis signaling pathway, promotes the progression of gliomas.

Identification of Tumor Antigens and Immune Landscape in Glioblastoma for mRNA Vaccine Development.

Background: Clinical benefits from standard therapies against glioblastoma (GBM) are limited in part due to the intrinsic radio- and chemo-resistance. As an essential part of tumor immunotherapy for adjunct, therapeutic tumor vaccines have been effective against multiple solid cancers, while their efficacy against GBM remains undefined. Therefore, this study aims to find the possible tumor antigens of GBM and identify the suitable population for cancer vaccination through immunophenotyping. Method: The genomic and responding clinical data of 169 GBM samples and five normal brain samples were obtained from The Cancer Genome Atlas (TCGA). The mRNA_seq data of 940 normal brain tissue were downloaded from Genotype-Tissue Expression (GTEx). Potential GBM mRNA antigens were screened out by differential expression, copy number variant (CNV), and mutation analysis. K-M survival and Cox analysis were carried out to investigate the prognostic association of potential tumor antigens. Tumor Immune Estimation Resource (TIMER) was used to explore the association between the antigens and tumor immune infiltrating cells (TIICs). Immunophenotyping of 169 samples was performed through consensus clustering based on the abundance of 22 kinds of immune cells. The characteristics of the tumor immune microenvironment (TIME) in each cluster were explored through single-sample gene set enrichment analysis based on 29 kinds of immune-related hallmarks and pathways. Weighted gene co-expression network analysis (WGCNA) was performed to cluster the genes related to immune subtypes. Finally, pathway enrichment analyses were performed to annotate the potential function of modules screened through WGCNA. Results: Two potential tumor antigens selected were significantly positively associated with the antigen-presenting immune cells (APCs) in GBM. Furthermore, the expression of antigens was verified at the protein level by Immunohistochemistry. Two robust immune subtypes, immune subtype 1 (IS1) and immune subtype 2 (IS2), representing immune status "immune inhibition" and "immune inflamed", respectively, had distinct clinical outcomes in GBM. Conclusion: ARPC1B and HK3 were potential mRNA antigens for developing GBM mRNA vaccination, and the patients in IS2 were considered the most suitable population for vaccination in GBM.

Identification of tumor antigens and immune subtypes in lower grade gliomas for mRNA vaccine development.

BACKGROUND: As an important part of tumor immunotherapy for adjunct, therapeutic tumor vaccines have been effective against multiple solid cancers, while their efficacy against lower grade glioma (LGG) remains undefined. Immunophenotyping of tumors is an essential tool to evaluate the immune function of patients with immunodeficiency or autoimmunity. Therefore, this study aims to find the potential tumor antigen of LGG and identify the suitable population for cancer vaccination based on the immune landscape. METHOD: The genomic and clinical data of 529 patients with LGG were obtained from TCGA, the mRNA_seq data of normal brain tissue were downloaded from GTEx. Differential expression gene and mutation analysis were performed to screen out potential antigens, K-M curves were carried out to investigate the correlation between the level of potential antigens and OS and DFS of patients. TIMER dataset was used to explore the correlation between genes and immune infiltrating cells. Immunophenotyping of 529 tumor samples was based on the single-sample gene sets enrichment analysis. Cibersort and Estimate algorithm were used to explore the tumor immune microenvironment characteristics in each immune subtype. Weighted gene co-expression network analysis (WGCNA) clustered immune-related genes and screened the hub genes, and pathway enrichment analyses were performed on the hub modules related to immune subtype in the WGCNA. RESULTS: Selecting for the mutated, up-regulated, prognosis- and immune-related genes, four potential tumor antigens were identified in LGG. They were also significantly positively associated with the antigen-presenting immune cells (APCs). Three robust immune subtypes, IS1, IS2 and IS3, represented immune status "desert", "immune inhibition", and "inflamed" respectively, which might serve as a predictive parameter. Subsequently, clinicopathological features, including the codeletion status of 1p19q, IDH mutation status, tumor mutation burden, tumor stemness, etc., were significantly different among subtypes. CONCLUSION: FCGBP, FLNC, TLR7, and CSF2RA were potential antigens for developing cancer vaccination, and the patients in IS3 were considered the most suitable for vaccination in LGG.

Site-Selective Functionalization of (sp3 )C-H Bonds Catalyzed by Artificial Metalloenzymes Containing an Iridium-Porphyrin Cofactor.

The selective functionalization of one C-H bond over others in nearly identical steric and electronic environments can facilitate the construction of complex molecules. We report site-selective functionalizations of C-H bonds, differentiated solely by remote substituents, catalyzed by artificial metalloenzymes (ArMs) that are generated from the combination of an evolvable P450 scaffold and an iridium-porphyrin cofactor. The generated systems catalyze the insertion of carbenes into the C-H bonds of a range of phthalan derivatives containing substituents that render the two methylene positions in each phthalan inequivalent. These reactions occur with site-selectivity ratios of up to 17.8:1 and, in most cases, with pairs of enzyme mutants that preferentially form each of the two constitutional isomers. This study demonstrates the potential of abiotic reactions catalyzed by metalloenzymes to functionalize C-H bonds with site selectivity that is difficult to achieve with small-molecule catalysts.

Beyond Iron: Iridium-Containing P450 Enzymes for Selective Cyclopropanations of Structurally Diverse Alkenes.

Enzymes catalyze organic transformations with exquisite levels of selectivity, including chemoselectivity, stereoselectivity, and substrate selectivity, but the types of reactions catalyzed by enzymes are more limited than those of chemical catalysts. Thus, the convergence of chemical catalysis and biocatalysis can enable enzymatic systems to catalyze abiological reactions with high selectivity. Recently, we disclosed artificial enzymes constructed from the apo form of heme proteins and iridium porphyrins that catalyze the insertion of carbenes into a C-H bond. We postulated that the same type of Ir(Me)-PIX enzymes could catalyze the cyclopropanation of a broad range of alkenes with control of multiple modes of selectivity. Here, we report the evolution of artificial enzymes that are highly active and highly stereoselective for the addition of carbenes to a wide range of alkenes. These enzymes catalyze the cyclopropanation of terminal and internal, activated and unactivated, electron-rich and electron-deficient, conjugated and nonconjugated alkenes. In particular, Ir(Me)-PIX enzymes derived from CYP119 catalyze highly enantio- and diastereoselective cyclopropanations of styrene with ±98% ee, >70:1 dr, >75% yield, and ∼10,000 turnovers (TON), as well as 1,2-disubstituted styrenes with up to 99% ee, 35:1 dr, and 54% yield. Moreover, Ir(Me)-PIX enzymes catalyze cyclopropanation of internal, unactivated alkenes with up to 99% stereoselectivity, 76% yield, and 1300 TON. They also catalyze cyclopropanation of natural products with diastereoselectivities that are complementary to those attained with standard transition metal catalysts. Finally, Ir(Me)-PIX P450 variants react with substrate selectivity that is reminiscent of natural enzymes; they react preferentially with less reactive internal alkenes in the presence of more reactive terminal alkenes. Together, the studies reveal the suitability of Ir-containing P450s to combine the broad reactivity and substrate scope of transition metal catalysts with the exquisite selectivity of enzymes, generating catalysts that enable reactions to occur with levels and modes of activity and selectivity previously unattainable with natural enzymes or transition metal complexes alone.