Peptide Drug Design Using Alchemical Free Energy Calculation: An Application and Validation on Agonists of Ghrelin Receptor.

With recent large-scale applications and validations, the relative binding free energy (RBFE) calculated using alchemical free energy methods has been proven to be an accurate measure to probe the binding of small-molecule drug candidates. On the other hand, given the flexibility of peptides, it is of great interest to find out whether sufficient sampling could be achieved within the typical time scale of such calculation, and a similar level of accuracy could be reached for peptide drugs. However, the systematic evaluation of such calculations on protein-peptide systems has been less reported. Most reported studies of peptides were restricted to a limited number of data points or lacking experimental support. To demonstrate the applicability of the alchemical free energy method for protein-peptide systems in a typical real-world drug discovery project, we report an application of the thermodynamic integration (TI) method to the RBFE calculation of ghrelin receptor and its peptide agonists. Along with the calculation, the synthesis and in vitro EC50 activity of relamorelin and 17 new peptide derivatives were also reported. A cost-effective criterion to determine the data collection time was proposed for peptides in the TI simulation. The average of three TI repeats yielded a mean absolute error of 0.98 kcal/mol and Pearson's correlation coefficient (R) of 0.77 against the experimental free energy derived from the in vitro EC50 activity, showing good repeatability of the proposed method and a slightly better agreement than the results obtained from the arbitrary time frames up to 20 ns. Although it is limited by having one target and a deduced binding pose, we hope that this study can add some insights into alchemical free energy calculation of protein-peptide systems, providing theoretical assistance to the development of peptide drugs.

Fe-N hollow mesoporous carbon spheres with high oxidase-like activity for sensitive detection of alkaline phosphatase.

Due to the vital role of alkaline phosphatase (ALP) in clinical diagnoses and biomedical research, a sensitive and selective detection method for ALP activity is of considerable importance. Herein, a facile and sensitive colorimetric assay for the detection of ALP activity was developed based on Fe-N hollow mesoporous carbon spheres (Fe-N HMCS). Fe-N HMCS were synthesized by a practical one-pot method with aminophenol/formaldehyde (APF) resin as the carbon/nitrogen precursor, silica as the template and iron phthalocyanine (FePC) as the iron source. Thanks to the highly dispersed Fe-N active sites, Fe-N HMCS exhibited exceptional oxidase-like activity. In the presence of dissolved oxygen, Fe-N HMCS were able to effectively convert colorless 3,3',5,5'-tetramethylbenzidine (TMB) into oxidized TMB (oxTMB) with blue color, while the reducing agent of ascorbic acid (AA) inhibited the color reaction. Based on this fact, an indirect and sensitive colorimetric sensing method was developed to detect alkaline phosphatase (ALP) with the assistance of the substrate L-ascorbate 2-phosphate (AAP). This ALP biosensor exhibited a linear range of 1-30 U L-1 and a limit of detection (LOD) of 0.42 U L-1 in standard solutions. In addition, this method was applied to detect ALP activity in human serum with satisfactory results. This work offers a positive reference for the reasonable excavation of transition metal-N carbon compounds in ALP-extended sensing applications.

TRIM32 biallelic defects cause limb-girdle muscular dystrophy R8: identification of two novel mutations and investigation of genotype-phenotype correlation.

BACKGROUND: Limb-girdle muscular dystrophy R8 (LGMD R8) is a rare autosomal recessive muscle disease caused by TRIM32 gene biallelic defects. The genotype-phenotype correlation of this disease has been reported poorly. Here, we report a Chinese family with two female LGMD R8 patients. METHODS: We performed whole-genome sequencing (WGS) and Sanger sequencing on the proband. Meanwhile, the function of mutant TRIM32 protein was analyzed by bioinformatics and experimental analysis. In addition, a summary of the reported TRIM32 deletions and point mutations and an investigation of genotype-phenotype correlation were performed through a combined analysis of the two patients and other cases reported in previous literature. RESULTS: The two patients displayed typical symptoms of LGMD R8, which worsened during pregnancy. Genetic analysis by whole-genome sequencing (WGS) and Sanger sequencing showed that the patients were compound heterozygotes of a novel deletion (chr9.hg19:g.119431290_119474250del) and a novel missense mutation (TRIM32:c.1700A > G, p.H567R). The deletion encompassed 43 kb and resulted in the removal of the entire TRIM32 gene. The missense mutation altered the structure and further affected function by interfering with the self-association of the TRIM32 protein. Females with LGMD R8 showed less severe symptoms than males, and patients carrying two mutations in NHL repeats of the TRIM32 protein had earlier disease onset and more severe symptoms than other patients. CONCLUSIONS: This research extended the spectrum of TRIM32 mutations and firstly provided useful data on the genotype-phenotype correlation, which is valuable for the accurate diagnosis and genetic counseling of LGMD R8.

Dearomative [4 + 2] Annulation of Electron-Poor N-Heteroarenes with Azoalkenes for Access to Polycyclic Tetrahydro-1,2,4-triazines.

A direct dearomative [4 + 2] annulation of electron-poor N-heteroarenes with azoalkenes generated in situ from α-halogeno hydrazones was developed under mild conditions. Accordingly, a series of fused polycyclic tetrahydro-1,2,4-triazines with potential biological activity were obtained in up to 96% yield. Various α-halogeno hydrazones and N-heteroarenes, such as pyridines, quinolines, isoquinolines, phenanthridine, and benzothiazole, were tolerated by this reaction. The general applicability of this method was shown by upscale synthesis and product derivatization.

Reduced mitochondrial size in hippocampus and psychiatric behavioral changes in the mutant mice with homologous mutation of Timm8a1-I23fs49X.

Background: Deafness-dystonia-optic neuronopathy (DDON) syndrome, a condition that predominantly affects males, is caused by mutations in translocase of mitochondrial inner membrane 8A (TIMM8A)/deafness dystonia protein 1 (DDP1) gene and characterized by progressive deafness coupled with other neurological abnormalities. In a previous study, we demonstrated the phenotype of male mice carrying the hemizygous mutation of Timm8a1-I23fs49X. In a follow-up to that study, this study aimed to observe the behavioral changes in the female mutant (MUT) mice with homologous mutation of Timm8a1 and to elucidate the underlying mechanism for the behavioral changes. Materials and methods: Histological analysis, transmission electron microscopy (EM), Western blotting, hearing measurement by auditory brainstem response (ABR), and behavioral observation were compared between the MUT mice and wild-type (WT) littermates. Results: The weight of the female MUT mice was less than that of the WT mice. Among MUT mice, both male and female mice showed hearing impairment, anxiety-like behavior by the elevated plus maze test, and cognitive deficit by the Morris water maze test. Furthermore, the female MUT mice exhibited coordination problems in the balance beam test. Although the general neuronal loss was not found in the hippocampus of the MUT genotype, EM assessment indicated that the mitochondrial size showing as aspect ratio and form factor in the hippocampus of the MUT strain was significantly reduced compared to that in the WT genotype. More importantly, this phenomenon was correlated with the upregulation of translation of mitochondrial fission process protein 1(Mtfp1)/mitochondrial 18 kDa protein (Mtp18), a key fission factor that is a positive regulator of mitochondrial fission and mitochondrial size. Interestingly, significant reductions in the size of the uterus and ovaries were noted in the female MUT mice, which contributed to significantly lower fertility in the MUT mice. Conclusion: Together, a homologous mutation in the Timm8a1 gene caused the hearing impairment and psychiatric behavioral changes in the MUT mice; the latter phenotype might be related to a reduction in mitochondrial size regulated by MTP18.

Photo-induced catalytic halopyridylation of alkenes.

The Mizoroki-Heck reaction and its reductive analogue are staples of organic synthesis, but the ensuing products often lack a chemical handle for further transformation. Here we report an atom-economical cross-coupling of halopyridines and unactivated alkenes under photoredox catalysis to afford a series of alkene halopyridylation products. This protocol with mild and redox neutral conditions contributes broad substrate scope. As a complement to conventional Heck-type reaction, this radical process avoids the involvement of ß-H elimination and thus useful pyridyl and halide groups could be simultaneously and regioselectively incorporated onto alkenes. The success depends on TFA-promoted domino photocatalytic oxidative quenching activation and radical-polar crossover pathway. Plausible mechanism is proposed based on mechanistic investigations. Moreover, the reserved C - X bonds of these products are beneficial for performing further synthetic elaborations.

Charcot-Marie-Tooth Disease With Episodic Rhabdomyolysis Due to Two Novel Mutations in the ß Subunit of Mitochondrial Trifunctional Protein and Effective Response to Modified Diet Therapy.

A 29-year-old female experienced chronic progressive peripheral neuropathy since childhood and was diagnosed with Charcot-Marie-Tooth disease (CMT) at age 15. She developed recurrent, fever-induced rhabdomyolysis (RM) at age 24. EMG studies showed decreased amplitude of compound muscle action potential, declined motor conductive velocity, and absence of sensor nerve action potential. Acylcarnitine analysis revealed elevated C16-OH, C18-OH, and C18:1-OH. Muscle biopsy showed scattered foci of necrotic myofibers invaded by macrophages, occasional regenerating fibers, and remarkable muscle fiber type grouping. Whole-exome sequencing identified two novel heterozygous mutations: c.490G>A (p.G164S) and c.686G>A (p.R229Q) in HADHB gene encoding the ß-subunit of mitochondrial trifunctional protein (MTP). Reduction of long-chain fatty acid via dietary restrictions alleviated symptoms effectively. Our study indicates that the defect of the MTP ß-subunit accounts for both CMT and RM in the same patient and expands the clinical spectrum of disorders caused by the HADHB mutations. Our systematic review of all MTPD patients with dietary treatment indicates that the effect of dietary treatment is related to the age of onset and the severity of symptoms.

The serendipitous effect of KF in Ritter reaction: Photo-induced amino-alkylation of alkenes.

Ritter reaction has been recognized as an elegant strategy to construct the C-N bond. Its key feature is forming the carbocation for nucleophilic attack by nitriles. Herein, we report a complementary visible-light-induced three-component Ritter reaction of alkenes, nitriles, and α-bromo nitriles/esters, thereby providing mild and rapid access to various γ-amino nitriles/acids. Mechanistic studies indicated that traceless fluoride relay, transforming KF into imidoyl fluoride intermediate, is critical for the efficient reaction switch from atom transfer radical addition (ATRA) to the Ritter reaction. This approach to amino-alkylation of alkenes is chemoselective and operationally simple.

Visible Light Induced Bifunctional Rhodium Catalysis for Decarbonylative Coupling of Imides with Alkynes.

Transition metal catalyzed decarbonylation offers a distinct synthetic strategy for new chemical bond formation. However, the π-backbonding between CO π* orbitals and metal center d-orbitals impedes ligand dissociation to regenerate the catalyst under mild reaction conditions. Developed here is visible light induced rhodium catalysis for decarbonylative coupling of imides with alkynes under ambient conditions. Initial mechanistic studies suggest that the rhodium complex simultaneously serves as the catalytic center and photosensitizer for decarbonylation. This visible light promoted catalytic decarbonylation strategy offers new opportunities for reviewing old transformations with ligand dissociation as a rate-determining step.

Frameshift mutation of Timm8a1 gene in mouse leads to an abnormal mitochondrial structure in the brain, correlating with hearing and memory impairment.

BACKGROUND: Deafness-dystonia-optic neuronopathy (DDON) syndrome is a progressive X-linked recessive disorder characterised by deafness, dystonia, ataxia and reduced visual acuity. The causative gene deafness/dystonia protein 1 (DDP1)/translocase of the inner membrane 8A (TIMM8A) encodes a mitochondrial intermembrane space chaperon. The molecular mechanism of DDON remains unclear, and detailed information on animal models has not been reported yet. METHODS AND RESULTS: We characterized a family with DDON syndrome, in which the affected members carried a novel hemizygous variation in the DDP1 gene (NM_004085.3, c.82C>T, p.Q28X). We then generated a mouse line with the hemizygous mutation (p.I23fs49X) in the Timm8a1 gene using the clustered regularly interspaced short palindromic repeats /Cas9 technology. The deficient DDP1 protein was confirmed by western blot assay. Electron microscopic analysis of brain samples from the mutant mice indicated abnormal mitochondrial structure in several brain areas. However, Timm8a1I23fs49X/y mutation did not affect the import of mitochondria inner member protein Tim23 and outer member protein Tom40 as well as the biogenesis of the proteins in the mitochondrial oxidative phosphorylation system and the manganese superoxide dismutase (MnSOD / SOD-2). The male mice with Timm8a1I23fs49X/y mutant exhibited less weight gain, hearing impairment and cognitive deficit. CONCLUSION: Our study suggests that frameshift mutation of the Timm8a1 gene in mice leads to an abnormal mitochondrial structure in the brain, correlating with hearing and memory impairment. Taken together, we have successfully generated a mouse model bearing loss-of-function mutation in Timm8a1.

Graft-vs-Host Disease-Induced Hyperthyroidism in a Recipient of Allogeneic Hematopoietic Stem Cell Transplantation: A Case Report.

BACKGROUND: Hyperthyroidism after hematopoietic stem cell transplantation (HSCT) is rare, and only a few cases have been reported. What is more important, the fundamental mechanisms of hyperthyroidism after HSCT remained unclear. CASE: A 28-year-old man received an HLA haploidentical related-donor HSCT for acute myeloid leukemia and developed hyperthyroidism 31 months after HSCT. He presented with periodic paralysis as the initial symptom, his serum levels of free triiodothyronine (fT3), free thyroxine (fT4), and anti-thyroid autoantibodies increased, and thyroid-stimulating hormone level decreased. As a result, he was diagnosed with hyperthyroidism. Although systemic symptoms, signs, and laboratory findings of graft-vs-host disease (GVHD) were absent, thyroid histopathologic examination revealed thyroid follicular destruction and infiltrations of lymphocytes, which mainly consisted of CD20+ B lymphocytes and CD4+ and CD3+ T lymphocytes by immunohistochemistry. These were in accordance with the pathologic features of GVHD. The symptom of periodic paralysis resolved after treatment with prednisolone and methimazole for 1 month. The treatments lasted for 4 months, and the plasma levels of fT3, fT4, TSH, and anti-thyroid peroxidase normalized. He did not relapse after drug withdrawal with observation for 24 months to date. CONCLUSIONS: To the best of our knowledge, the present case was the first to be confirmed with thyroid-specific GVHD-induced hyperthyroidism after allogeneic HSCT.

Phosphatidylserine-exposing blood cells, microparticles and neutrophil extracellular traps increase procoagulant activity in patients with pancreatic cancer.

Patients with pancreatic cancer (PC) are at increased risk of venous thrombosis, but the precise mechanisms of hypercoagulable state in PC remain unclear. We aimed to identify how phosphatidylserine positive (PS+) blood cells (BCs), PS+ microparticles (MPs) and neutrophil extracellular traps (NETs) regulate procoagulant activity (PCA) in PC, and to assess the relationship between PCA and PC staging. A total of 83 PC patients with different stages of disease were compared to 30 healthy controls, with confocal microscopy and flow cytometry used to assess MP and cellular PS exposure. MP and cell PCA was determined using both fibrin production assays and procoagulant enzyme complex analyses, and coagulation time was further measured. Patients with stage I PC and healthy controls exhibited significantly lower frequencies of PS+ MPs and BCs relative to those with more advanced disease, which may partly due to the increased levels of inflammation cytokines in advanced disease. Functional coagulation assays indicated that PS+ MPs and BCs derived from patients with stage II/III/IV PC directly contribute to elevated FXa, thrombin, and fibrin formation, and to more rapid coagulation relative to healthy control samples. In inhibition assays, lactadherin, which antagonizes PS, led to a roughly 80% inhibition of PCA. We further used isolated NETs to stimulate endothelial cells, revealing that this led to morphological changes including retraction from cell-cell junctions and a more pro-coagulative phenotype, with DNase I and activated protein C treatment reversing these changes. In patients with stage III PC, curative resection surgery significantly reduced PCA, whereas non-curative surgery did not have a marked impact based on studies of pre- and post-operative samples. These results highlight the pathogenic activity of PS+ cells, MPs, and NETs in promoting a prothrombotic environment within individuals suffering from advanced PC. Targeting PS and NETs in these patients may thus be a viable means of preventing pathological thrombosis.

Rhodium-catalyzed asymmetric hydrogenation of exocyclic α,ß-unsaturated carbonyl compounds.

A highly enantioselective hydrogenation of exocyclic α,ß-unsaturated carbonyl compounds catalyzed by Rh/bisphosphine-thiourea (ZhaoPhos) has been developed, giving the corresponding α-chiral cyclic lactones, lactams and ketones with high yields and excellent enantioselectivities (up to 99% yield and 99% ee). Remarkably, the hydrogen bond between the substrate and the catalyst plays a critical role in this transformation. The synthetic utility of this protocol has been demonstrated by efficient synthesis of chiral 3-(4-fluorobenzyl)piperidine, a key chiral fragment of bioactive molecules.

Enantioselective Rhodium-Catalyzed Cycloisomerization of 1,6-Allenynes to access 5/6-Fused Bicycle[4.3.0]nonadienes.

Transition-metal-catalyzed cycloisomerization of 1,n-allenynes represents a powerful synthetic tool to rapidly assemble complex polycyclic skeletons from simple linear substrates. Nevertheless, there are no reports of the asymmetric version of these reactions. Moreover, most of these reactions proceed through a 6-endo-dig cyclization pathway, which preferentially delivers the distal product (via 5/5 rhodacyclic intermediate) rather than the proximal one (via 6/5 rhodacyclic intermediate). Herein, we report an enantioselective rhodium(I)-catalyzed cycloisomerization of 1,6-allenynes to provide the proximal product 5/6-fused bicycle[4.3.0]nonadienes in good yields and with excellent enantioselectivities. Remarkably, this chemistry works perfectly for 1,6-allenynes having a cyclic substituent within the allene component, thereby affording synthetically formidable tricyclic products with excellent enantioselectivities. Moreover, extensive DFT calculations suggest an uncommon pathway involving 5-exo-dig cycloisomerization, ring-expansion, rate-determining alkene isomerization involving Csp3-H activation, C-C activation of the cyclobutene moiety and finally reductive elimination. Deuterium labeling experiments support the rate-determining step involving the C-H bond activation in this transformation.

A cheap metal for a challenging task: nickel-catalyzed highly diastereo- and enantioselective hydrogenation of tetrasubstituted fluorinated enamides.

Nickel-catalyzed asymmetric hydrogenation of challenging tetrasubstituted fluorinated enamides has been achieved, affording chiral α-fluoro-ß-amino esters in high yields with excellent diastereo- and enantioselectivities (up to 98% yield, >99 : 1 dr, up to >99% ee). Deuterium-labeling experiments and control experiments were conducted to probe the mechanism, and the results indicated that the acidity of the solvent plays a critical role in the control of diastereoselectivity by trapping the adduct of nickel hydride to C[double bond, length as m-dash]C bonds via protonolysis, giving the hydrogenation product with stereospecific syn-selectivity. This protocol provides efficient access to chiral α-fluoro-ß-amino esters which have important potential applications in organic synthesis and medicinal chemistry.

Iridium-Catalyzed Asymmetric Hydrogenation of Tetrasubstituted α-Fluoro-ß-enamino Esters: Efficient Access to Chiral α-Fluoro-ß-amino Esters with Two Adjacent Tertiary Stereocenters.

An iridium-catalyzed highly efficient asymmetric hydrogenation of challenging tetrasubstituted α-fluoro-ß-enamino esters was successfully developed using bisphosphine-thiourea (ZhaoPhos) as the ligand, which prepared a series of chiral α-fluoro-ß-amino esters containing two adjacent tertiary stereocenters with high yields and excellent diastereoselectivities/enantioselectivities (73%-99% yields, >25:1 dr, 91%->99% ee, and turnover number (TON) values up to 8600), and no defluorinate byproduct was detected.

Nickel-Catalyzed Highly Enantioselective Hydrogenation of ß-Acetylamino Vinylsulfones: Access to Chiral ß-Amido Sulfones.

The nickel/( S)-Binapine complex was found to be an efficient catalyst for asymmetric hydrogenation of ß-acetylamino vinylsulfones to afford chiral ß-Amido sulfones with excellent yields and enantioselectivities (up to 95% yields and >99% ee). This protocol has good compatibility with a series of substituted ( Z)-ß-acetylamino vinylsulfones or Z/ E isomeric mixtures. A gram-scale reaction has also been achieved in the presence of a 0.2 mol % catalyst loading.

Rhodium-catalyzed asymmetric hydrogenation of tetrasubstituted ß-acetoxy-α-enamido esters and efficient synthesis of droxidopa.

A rhodium-catalyzed asymmetric hydrogenation of challenging tetrasubstituted ß-acetoxy-α-enamido esters was developed, giving chiral ß-acetoxy-α-amido esters in high yields with excellent enantioselectivities (up to >99% ee). The products could be easily transformed to ß-hydroxy-α-amino acid derivatives which are valuable chiral building blocks and a novel route for the synthesis of droxidopa was also developed.

Enantioselective Rhodium-Catalyzed Cycloisomerization of (E)-1,6-Enynes.

An enantioselective rhodium(I)-catalyzed cycloisomerization reaction of challenging (E)-1,6-enynes is reported. This novel process enables (E)-1,6-enynes with a wide range of functionalities, including nitrogen-, oxygen-, and carbon-tethered (E)-1,6-enynes, to undergo cycloisomerization with excellent enantioselectivity, in a high-yielding and operationally simple manner. Moreover, this Rh(I) -diphosphane catalytic system also exhibited superior reactivity and enantioselectivity for (Z)-1,6-enynes. A rationale for the striking reactivity difference between (E)- and (Z)-1,6-enynes using Rh(I) -BINAP and Rh(I) -TangPhos is outlined using DFT studies to provide the necessary insight for the design of new catalyst systems and the application to synthesis.