Clinical impact and characteristics of erythroid dysplasia in adult aplastic anaemia: Results from a multicentre registry.

Morphological dysplasia in haematopoietic cells, defined by a 10% threshold in each lineage, is one of the diagnostic criteria for myelodysplastic neoplasms. Dysplasia limited to the erythroid lineage has also been reported in some cases of aplastic anaemia (AA); however, its significance remains unclear. We herein examined the impact of erythroid dysplasia on immunosuppressive therapy responses and survival in AA patients. The present study included 100 eligible AA patients without ring sideroblasts. Among them, 32 had dysplasia in the erythroid lineage (AA with minimal dysplasia [mini-D]). No significant sex or age differences were observed between AA groups with and without erythroid dysplasia. In severe/very severe AA and non-severe AA patients, a response to anti-thymocyte globulin + ciclosporin within 12 months was observed in 80.0% and 60.0% of AA with mini-D and 42.9% and 90.0% of those without dysplasia, with no significant difference (p = 0.29 and p = 0.24 respectively). Overall survival and leukaemia-free survival did not significantly differ between the groups. Collectively, the present results indicate that the presence of erythroid dysplasia did not significantly affect clinical characteristics or outcomes in AA patients, suggesting that its presence in AA is acceptable. Therefore, erythroid dysplasia should not exclude an AA diagnosis.

Weak response of bovine hepcidin induction to iron through decreased expression of Smad4.

Hepcidin negatively regulates systemic iron levels by inhibiting iron entry into the circulation. Hepcidin production is increased in response to an increase in systemic iron via the activation of the bone morphogenetic protein (BMP) pathway. Regulation of hepcidin expression by iron status has been proposed on the basis of evidence mainly from rodents and humans. We evaluated the effect of iron administration on plasma hepcidin concentrations in calves and the expression of bovine hepcidin by the BMP pathway in a cell culture study. Hematocrit as well as levels of blood hemoglobin and plasma iron were lower than the reference level in calves aged 1-4 weeks. Although intramuscular administration of iron increased iron-related parameters, plasma hepcidin concentrations were unaffected. Treatment with BMP6 increased hepcidin expression in human liver-derived cells but not in bovine liver-derived cells. A luciferase-based reporter assay revealed that Smad4 was required for hepcidin reporter transcription induced by Smad1. The reporter activity of hepcidin was lower in the cells transfected with bovine Smad4 than in those transfected with murine Smad4. The lower expression levels of bovine Smad4 were responsible for the lower activity of the hepcidin reporter, which might be due to the instability of bovine Smad4 mRNA. In fact, the endogenous Smad4 protein levels were lower in bovine cells than in human and murine cells. Smad4 also confers TGF-ß/activin-mediated signaling. Induction of TGF-ß-responsive genes was also lower after treatment with TGF-ß1 in bovine hepatocytes than in human hepatoma cells. We revealed the unique regulation of bovine hepcidin expression and the characteristic TGF-ß family signaling mediated by bovine Smad4. The present study suggests that knowledge of the regulatory expression of hepcidin as well as TGF-ß family signaling obtained in murine and human cells is not always applicable to bovine cells.

[Evaluation of oral medications in the geriatric medical care ward based on the Guidelines for Appropriate Use of Medications for the Elderly (2018), and an analysis of the number of oral medicines in relation to the nutritional route and activities of daily living (ADL) categories].

AIM: This study aimed to evaluate the use of potentially inappropriate medications (PIMs) and to examine the number of oral medicines based on the swallowing function and activities of daily living (ADL) categories in a geriatric medical care ward. METHODS: A prospective investigation of oral medication use of 124 consecutive patients (male, n=58; female, n=66) admitted to a geriatric medical care ward was conducted from November 2019 to October 2020. Nutritional routes and ADL categories were quantitatively assessed, and the respective medication quantities were subjected to a statistical analysis. RESULTS: The average number of oral medications was 5.8 at acute care admission, 4.4 upon transfer to the geriatric medical care ward and 4.8 at discharge. Approximately 30% of oral medications were classified as PIMs, including antithrombotic agents, diuretics, antidiabetic drugs, magnesium oxide, sleep and anxiolytic medications, and antipsychotic drugs. Magnesium oxide, antipsychotic drugs, sleep and anxiolytic medications were frequently discontinued during the patient's stay at the geriatric medical care ward. The proportion of PIMs significantly decreased from 35.1% at admission, to 28.8% at ward transfer, and 24.3% at discharge (P<0.01). The number of oral medicines at discharge varied based on the nutritional route, with averages of 5.5 for oral intake, 3.6 for enteral nutrition, and 0.7 for venous nutrition. It also varied based on ADL categories, with averages of 6.0 for ADL 1, 5.8 for ADL 2, and 3.8 for ADL 3. CONCLUSION: The use of PIMs decreased in the geriatric medical care ward. A reduced swallowing function and lower ADL were associated with a decrease in the quantity of oral medicines.

A tetravalent peptide that binds to the RANK-binding region of TRAF6 via a multivalent interaction efficiently inhibits osteoclast differentiation.

Inhibition of osteoclast differentiation is a promising approach for the treatment of osteoporosis and rheumatoid arthritis. Receptor activator of nuclear factor kappa B (NF-κB) (RANK), which is an essential molecule for osteoclast differentiation, interacts with tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) to transduce downstream signals. Both RANK and TRAF6 have homo-trimeric structures, forming a multivalent interaction between the Pro-X-Glu-X-X-(aromatic/acidic) motif of RANK and the C-terminal domain of TRAF6 (TRAF-C), that markedly increases the binding affinity. Here, we designed a tetravalent peptide, RANK-tet, containing the TRAF-C-binding motif of RANK and found that RANK-tet binds to TRAF-C with high affinity. In contrast, a monomeric form of RANK-tet (RANK-mono) with the same TRAF-C-binding motif did not bind to TRAF-C, clearly indicating the multivalent interaction is strictly required for the high-affinity binding to TRAF-C. RANK-tet did not bind to a series of TRAF-C-mutants with an amino acid substitution in the RANK-binding region, indicating that RANK-tet specifically targets the RANK-binding region of TRAF-C. A cell-permeable form of RANK-tet that has poly-Arg residues at each C-terminal of the TRAF-C-binding motif efficiently inhibited the RANK ligand (RANKL)-induced differentiation of bone marrow cells to osteoclasts. Thus, this compound can be an effective anti-osteoclastogenic agent.

Castleman disease and TAFRO syndrome.

Although Castleman disease was first described in 1956, this disease includes various conditions, including unicentric Castleman disease with hyaline vascular histology, human herpesvirus-8 (HHV-8) related multicentric Castleman disease, idiopathic multicentric Castleman disease, and mimics of Castleman disease associated with other conditions. To date, Castleman disease remains incompletely understood due to its rareness and difficulties in clinical and pathological diagnosis. TAFRO syndrome was reported in Japan in 2010. Because lymph node histology is similar in patients with TAFRO syndrome and Castleman disease, TAFRO syndrome is described as a related disorder of Castleman disease. Clinically, however, these conditions differ markedly. Although elevated interleukin-6 (IL-6) expression is characteristic of Castleman disease, increased expression of IL-6 may occur in patients with other diseases, making elevated IL-6 unsuitable for differential diagnosis. Further understanding of these disorders requires the identification of novel disease-specific biomarkers. This review article therefore outlines the characteristics of Castleman disease and TAFRO syndrome.

Recycled ancient ghost carbonate in the Pitcairn mantle plume.

The extreme Sr, Nd, Hf, and Pb isotopic compositions found in Pitcairn Island basalts have been labeled enriched mantle 1 (EM1), characterizing them as one of the isotopic mantle end members. The EM1 origin has been vigorously debated for over 25 years, with interpretations ranging from delaminated subcontinental lithosphere, to recycled lower continental crust, to recycled oceanic crust carrying ancient pelagic sediments, all of which may potentially generate the requisite radiogenic isotopic composition. Here we find that δ26Mg ratios in Pitcairn EM1 basalts are significantly lower than in normal mantle and are the lowest values so far recorded in oceanic basalts. A global survey of Mg isotopic compositions of potentially recycled components shows that marine carbonates constitute the most common and typical reservoir invariably characterized by extremely low δ26Mg values. We therefore infer that the subnormal δ26Mg of the Pitcairn EM1 component originates from subducted marine carbonates. This, combined with previously published evidence showing exceptionally unradiogenic Pb as well as sulfur isotopes affected by mass-independent fractionation, suggests that the Pitcairn EM1 component is most likely derived from late Archean subducted carbonate-bearing sediments. However, the low Ca/Al ratios of Pitcairn lavas are inconsistent with experimental evidence showing high Ca/Al ratios in melts derived from carbonate-bearing mantle sources. We suggest that carbonate-silicate reactions in the late Archean subducted sediments exhausted the carbonates, but the isotopically light magnesium of the carbonate was incorporated in the silicates, which then entered the lower mantle and ultimately became the Pitcairn plume source.

Hydrogen Dissociation Dynamics from Water Clusters on Triplet-State Energy Surfaces.

The ice surface provides two-dimensional reaction fields for bimolecular collisions in interstellar space. As H2O molecules on the surface are typically exposed to cosmic rays, H2O in the excited state is easily dissociated into H + OH, where a H atom is released from the surface to the gas phase. In the present study, the reaction dynamics of small-sized water clusters on the triplet-state potential energy (T1) surface, following the vertical electronic excitation from the ground state (S0), were investigated using direct ab initio molecular dynamics to provide insights into the generation mechanism of H atoms from an irradiated ice surface. In all clusters, that is, (H2O)n (n = 2-6), the H atom was directly dissociated from one of the H2O molecules in the clusters (direct dissociation), whereas the OH radical remained in the cluster. In the branched form of H2O tetramer (n = 4) and the book form of H2O hexamer (n = 6), the dissociated hydrogen atom (H') collided with the neighboring H2O molecule, and the exchange of H atoms occurred as H' + H2O → H'-H2O (collision) → H'OH + H (hydrogen exchange). The translational energy of the exchanged H atom decreases significantly (by approximately 50%) because the kinetic energy of the H' atom is efficiently transferred to the vibrational modes of the cluster during the H-exchange reaction. The mechanism of H atom dissociation is discussed based on theoretical results.

[The pathogenesis of anemia in inflammation].

Inflammation is a physiological process that primarily occurs as a way to help protect the host against tissue damage and invasion by pathogens. During inflammation, erythropoiesis is suppressed and, if it lasts, anemia develops. The mechanisms underlying this are complex and not fully understood, but various cytokines, such as tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1ß (IL-1ß), and IL-6, are involved. TNF-α upregulates PU.1, which is a crucial transcription factor in granulocytic differentiation, and downregulates GATA-1, a master transcription factor for erythroid differentiation, in hematopoietic stem cells. TNF-α and IL-1ß suppress erythropoietin production in the kidney, whereas IFN-γ downregulates the expression of erythropoietin receptors in erythroid precursor cells. Moreover, IL-6 upregulates the production of hepcidin, the master regulator of systemic iron metabolism, in the liver. Hepcidin reduces the iron available for erythropoiesis by downregulating the rate of iron release from macrophages. Activated macrophages may also contribute to the development of anemia by shortening the erythrocyte lifespan. Proper management of the underlining conditions is necessary in treating anemia associated with inflammation. Erythropoiesis-stimulating agents may be administered to patients with chronic kidney disease, whereas anti-IL-6 agents may be beneficial for anemic patients with rheumatoid arthritis and idiopathic multicentric Castleman disease.

Pathogenic mutations identified by a multimodality approach in 117 Japanese Fanconi anemia patients.

Fanconi anemia is a rare recessive disease characterized by multiple congenital abnormalities, progressive bone marrow failure, and a predisposition to malignancies. It results from mutations in one of the 22 known FANC genes. The number of Japanese Fanconi anemia patients with a defined genetic diagnosis was relatively limited. In this study, we reveal the genetic subtyping and the characteristics of mutated FANC genes in Japan and clarify the genotype-phenotype correlations. We studied 117 Japanese patients and successfully subtyped 97% of the cases. FANCA and FANCG pathogenic variants accounted for the disease in 58% and 25% of Fanconi anemia patients, respectively. We identified one FANCA and two FANCG hot spot mutations, which are found at low percentages (0.04-0.1%) in the whole-genome reference panel of 3,554 Japanese individuals (Tohoku Medical Megabank). FANCB was the third most common complementation group and only one FANCC case was identified in our series. Based on the data from the Tohoku Medical Megabank, we estimate that approximately 2.6% of Japanese are carriers of disease-causing FANC gene variants, excluding missense mutations. This is the largest series of subtyped Japanese Fanconi anemia patients to date and the results will be useful for future clinical management.

Is TAFRO syndrome a subtype of idiopathic multicentric Castleman disease?

Castleman disease (CD) is a rare lymphoproliferative disorder that can be unicentric or multicentric. Multicentric CD (MCD) is further subdivided into human herpesvirus type-8-associated, POEMS syndrome-associated, and idiopathic (iMCD). TAFRO syndrome is a newly identified disorder of unknown etiology characterized by thrombocytopenia, anasarca, fever, reticulin myelofibrosis, renal dysfunction, and organomegaly. The TAFRO syndrome is sometimes regarded as a subtype of iMCD (TAFRO-iMCD), whereas iMCD without TAFRO syndrome is considered "not otherwise specified" (iMCD-NOS). However, a proportion of patients with TAFRO syndrome have been diagnosed without lymph node biopsies (TAFRO syndrome without proven iMCD; TAFRO-w/op-iMCD). To clarify the clinical features of iMCD-NOS, TAFRO-iMCD, and TAFRO-w/op-iMCD, we retrospectively analyzed 220 patients extracted from the database of the Multicenter Collaborative Retrospective Study for Establishing the Concept of TAFRO Syndrome. The patients included 87 with iMCD-NOS, 63 with TAFRO-iMCD, and 19 with TAFRO-w/op-iMCD. Patients in all three groups exhibited anemia, hypoalbuminemia, and elevated serum C-reactive protein and interleukin-6 levels. No significant differences in clinical, laboratory, and prognostic features were noted between the TAFRO-iMCD, and TAFRO-w/op-iMCD groups. However, the iMCD-NOS group exhibited polyclonal hyper-γ-globulinemia. The five-year survival rates of patients in the iMCD-NOS and TAFRO-involved groups were 100% and 66.5%, respectively (dropping markedly during the first few months in the latter). The iMCD-NOS and the TAFRO-iMCD samples typically showed plasma cell and mixed-type histologies, respectively. Thus, iMCD can be classified into two distinct subtypes, iMCD-NOS and TAFRO-iMCD. As such, TAFRO-iMCD and TAFRO-w/op-iMCD may be considered the same entity, requiring prompt diagnosis and intensive care.

Tentative diagnostic criteria and disease severity classification for Castleman disease: A report of the research group on Castleman disease in Japan.

OBJECTIVES: To determine the tentative diagnostic criteria and disease severity classification for Castleman disease (CD) and describe the clinical and pathologic features among human herpesvirus 8 (HHV-8) negative idiopathic multicentric CD (iMCD) in the Japanese population. METHODS: We established the working groups for the research of CD in Japan and had meetings to discuss and define the tentative diagnostic criteria and disease severity classification for CD. We subsequently analyzed 142 patients classified into iMCD by using the nationwide Japanese patient registry. RESULTS: We proposed the preliminary diagnostic criteria and disease severity classification for CD based on our discussion. In addition, we made a proposal for the disease activity score. We identified clinical and pathological features of patients with iMCD diagnosed by these diagnostic criteria. In the disease severity classification, 37, 33 and 30% patients were categorized into mild, moderate and severe diseases, respectively. CONCLUSION: This is the first proposal for diagnosis and classification of CD by the Japanese group. Further studies are required to validate whether they can distinguish CD from other inflammatory diseases and to determine their sensitivity and specificity.

[Myelodysplastic syndromes and iron metabolism].

Myelodysplastic syndromes (MDS) are clonal hematopoietic disorders characterized by ineffective hematopoiesis in bone marrow and cytopenias in peripheral blood. In patients with MDS, iron overload is frequent due to red blood cell transfusions and ineffective erythropoiesis. Dysplastic erythroblasts in MDS secrete humoral factors such as erythroferrone, which suppress hepatic expression of hepcidin. Hepcidin is the key regulator of systemic iron homeostasis, and suppression of hepcidin expression leads to an increase in iron absorption from the intestines, exacerbating systemic iron overload. Patients with MDS with ring sideroblasts (MDS-RS) are prone to iron overload, with most harboring splicing factor 3B subunit 1 (SF3B1) mutations in hematopoietic cells. SF3B1 mutations may induce ring sideroblasts by downregulating ATP binding cassette subfamily B member 7, which exports iron-sulfur clusters from the mitochondria to the cytoplasm. Iron overload in MDS causes hepatic dysfunction, diabetes, cardiac failure, and atherosclerosis, whereas excess iron may suppress normal hematopoiesis. Though randomized control studies are lacking, results from retrospective and cohort studies indicate that iron chelation therapy is appropriate for lower-risk MSD patients with transfusion-related iron overload, although it is not recommended for higher-risk MSD patients with short life expectancy.

Discovery of Lysine Hydroxylases in the Clavaminic Acid Synthase-Like Superfamily for Efficient Hydroxylysine Bioproduction.

Hydroxylation via C-H bond activation in the absence of any harmful oxidizing reagents is technically difficult in modern chemistry. In this work, we attempted to generate pharmaceutically important hydroxylysine from readily available l-lysine with l-lysine hydroxylases from diverse microorganisms. Clavaminic acid synthase-like superfamily gene mining and phylogenetic analysis led to the discovery of six biocatalysts, namely two l-lysine 3S-hydroxylases and four l-lysine 4R-hydroxylases, the latter of which partially matched known hydroxylases. Subsequent characterization of these hydroxylases revealed their capacity for regio- and stereoselective hydroxylation into either C-3 or C-4 positions of l-lysine, yielding (2S,3S)-3-hydroxylysine and (2S,4R)-4-hydroxylysine, respectively. To determine if these factors had industrial application, we performed a preparative production of both hydroxylysines under optimized conditions. For this, recombinant l-lysine hydroxylase-expressing Escherichia coli cells were used as a biocatalyst for l-lysine bioconversion. In batch-scale reactions, 531 mM (86.1 g/liter) (2S,3S)-3-hydroxylysine was produced from 600 mM l-lysine with an 89% molar conversion after a 52-h reaction, and 265 mM (43.0 g/liter) (2S,4R)-4-hydroxylysine was produced from 300 mM l-lysine with a molar conversion of 88% after 24 h. This report demonstrates the highly efficient production of hydroxylysines using lysine hydroxylases, which may contribute to future industrial bioprocess technologies.IMPORTANCE The present study identified six l-lysine hydroxylases belonging to the 2-oxoglutarate-dependent dioxygenase superfamily, although some of them overlapped with known hydroxylases. While the substrate specificity of l-lysine hydroxylases was relatively narrow, we found that (2S,3S)-3-hydroxylysine was hydroxylated by 4R-hydroxylase and (2S,5R)-5-hydroxylysine was hydroxylated by both 3S- and 4R-hydroxylases. Moreover, the l-arginine hydroxylase VioC also hydroxylated l-lysine, albeit to a lesser extent. Further, we also demonstrated the bioconversion of l-lysine into (2S,3S)-3-hydroxylysine and (2S,4R)-4-hydroxylysine on a gram scale under optimized conditions. These findings provide new insights into biocatalytic l-lysine hydroxylation and thus have a great potential for use in manufacturing bioprocesses.

A nationwide survey of hypoplastic myelodysplastic syndrome (a multicenter retrospective study).

Hypoplastic myelodysplastic syndrome (hMDS) is a distinct entity with bone marrow (BM) hypocellularity and the risk of death from BM failure (BMF). To elucidate the characteristics of hMDS, the data of 129 patients diagnosed between April 2003 and March 2012 were collected from 20 institutions and the central review team of the National Research Group on Idiopathic Bone Marrow Failure Syndromes, and compared with 115 non-hMDS patients. More RA and fewer CMMoL and RAEB-t in French-American-British (FAB) and more RCUD and MDS-U and fewer RCMD in World Health Organization (WHO) classifications were found in hMDS than non-hMDS with significant differences. The overall survival (OS) and AML progression-free survival (AML-PFS) of hMDS were higher than those of non-hMDS, especially in patients at age ≥50 and of lower risk in Revised International Prognostic Scoring System (IPSS-R). In competing risks analysis, hMDS exhibited decreased risk of AML-progression in lower IPSS or IPSS-R risk patients, and higher risk of death from BMF in patients at age ≥50. Poor performance status (PS ≥2) and high karyotype risks in IPSS-R (high and very high) were significant risk factors of death and AML-progression in Cox proportional hazards analysis.

Safe and effective administration of BCG for bladder carcinoma in situ after umbilical cord blood stem cell transplantation.

Although intravesical Bacillus Calmette-Guérin (BCG) instillation is the standard treatment for carcinoma in situ of the bladder, it is generally contraindicated in immunocompromised patients. Here we report the first case, to our knowledge, of BCG treatment for a bladder cancer patient who had received umbilical cord blood stem cell transplantation (UCBSCT). BCG can be given safely and effectively in select cases where reconstitution of the immune system has been achieved at least 2 years after UCBSCT.

Progress in iron metabolism research.

Iron is essential for various cellular processes, but an excess of iron may cause organ damage through the production of reactive oxygen species. Therefore, the amount of iron in the body must be strictly controlled. The central regulator of systemic iron homeostasis is hepcidin, which is primarily produced in the liver. Various molecules, including HFE, transferrin receptor 2 (TFR2), and hemojuvelin (HJV), are involved in sensing systemic iron status. Hepatocytes produce hepcidin in response to excess iron and inflammatory stimuli (e.g., interleukin-6), whereas hepcidin expression is downregulated by hypoxia, anemia, and erythropoietic activity. In mice, erythroferrone, secreted from erythroblasts, suppresses hepcidin expression. Hepcidin downregulates the protein expression of ferroportin, the only iron exporter in mammalian cells, and thereby downregulates iron absorption from intestine and iron release from macrophages. Mutations in the genes HFE, TFR2, HJV, HAMP (encoding hepcidin), and SLC40A1 (encoding ferroportin) cause hereditary hemochromatosis, whereas mutations in TMPRSS6 (which encodes matriptase 2) cause iron-refractory iron deficiency anemia through the upregulation of hepcidin expression. In chronic anemias, such as ß-thalassemia, myelodysplastic syndromes, and aplastic anemia, repeated red blood cell transfusion can cause systemic iron overload. Iron chelation therapy improves the prognosis of patients with such conditions.

Novel Enzyme Family Found in Filamentous Fungi Catalyzing trans-4-Hydroxylation of L-Pipecolic Acid.

Hydroxypipecolic acids are bioactive compounds widely distributed in nature and are valuable building blocks for the organic synthesis of pharmaceuticals. We have found a novel hydroxylating enzyme with activity toward L-pipecolic acid (L-Pip) in a filamentous fungus, Fusarium oxysporum c8D. The enzyme L-Pip trans-4-hydroxylase (Pip4H) of F. oxysporum (FoPip4H) belongs to the Fe(II)/α-ketoglutarate-dependent dioxygenase superfamily, catalyzes the regio- and stereoselective hydroxylation of L-Pip, and produces optically pure trans-4-hydroxy-L-pipecolic acid (trans-4-L-HyPip). Amino acid sequence analysis revealed several fungal enzymes homologous with FoPip4H, and five of these also had L-Pip trans-4-hydroxylation activity. In particular, the homologous Pip4H enzyme derived from Aspergillus nidulans FGSC A4 (AnPip4H) had a broader substrate specificity spectrum than other homologues and reacted with the L and D forms of various cyclic and aliphatic amino acids. Using FoPip4H as a biocatalyst, a system for the preparative-scale production of chiral trans-4-L-HyPip was successfully developed. Thus, we report a fungal family of L-Pip hydroxylases and the enzymatic preparation of trans-4-L-HyPip, a bioactive compound and a constituent of secondary metabolites with useful physiological activities.

Molecular Design of Ionization-Induced Proton Switching Element Based on Fluorinated DNA Base Pair.

To design theoretically the high-performance proton switching element based on DNA base pair, the effects of fluorine substitution on the rate of proton transfer (PT) in the DNA model base pair have been investigated by means of direct ab initio molecular dynamics (AIMD) method. The 2-aminopyridine dimer, (AP)2, was used as the model of the DNA base pair. One of the hydrogen atoms of the AP molecule in the dimer was substituted by a fluorine (F) atom, and the structures of the dimer, expressed by F-(AP)2, were fully optimized at the MP2/6-311++G(d,p) level. The direct AIMD calculations showed that the proton is transferred within the base pair after the vertical ionization. The rates of PT in F-(AP)2(+) were calculated and compared with that of (AP)2(+) without an F atom. It was found that PT rate is accelerated by the F-substitution. Also, the direction of PT between F-AP and AP molecules can be clearly controlled by the position of F-substitution (AP)2 in the dimer.

Effects of a Single Water Molecule on the Reaction Barrier of Interstellar CO2 Formation Reaction.

The mechanism by which CO2 is formed in the interstellar space remains a mystery. The most likely reaction is collision between CO and OH; however, previous theoretical works have shown that the activation barrier for CO2 formation is high enough to prevent the reaction at the low thermal conditions of space (∼10 K). The effects of single water molecule on the reaction barrier of CO2 formation from reaction between CO and OH have been investigated here by means of ab initio calculation. The barrier height along the lowest-energy pathway in the reaction between CO and OH in the absence of the H2O molecule was calculated to be 2.3 kcal/mol when CCSD(T) energy corrections are combined with the MP2 basis set limit. In the case of the hydrated (H2O-CO-OH) system, the inclusion of a single H2O molecule into the system significantly decreased the barrier height to 0.2 kcal/mol. This suggests that CO2 can be formed when CO and OH react in the presence of H2O, even under thermal conditions as low as 10 K.