Alpha/Beta Gliadin MM1 Is a Novel Antigen for Wheat-Dependent Exercise-Induced Anaphylaxis.

INTRODUCTION: Screening for ω-5 gliadin specific IgE antibody (sIgE) has high diagnostic utility in cases of suspected wheat-dependent exercise-induced anaphylaxis (WDEIA); however, negative cases may require confirmatory tests, such as the oral challenge test. Thus, newly identified allergens that can be used for the serological diagnosis of WDEIA are needed. This study aimed to identify additional sIgE biomarkers of WDEIA. METHODS: Forty-two patients with WDEIA (5 negative/37 positive for ω-5 gliadin sIgE) were enrolled. For comparison, 8 patients with immediate-type wheat allergy without WDEIA and 20 healthy controls without wheat allergy were also enrolled. Extracted wheat proteins were separated by 2D-PAGE. Proteins that reacted with serum IgE antibody in 2D Western blotting (2D-WB) were identified using mass spectrometry. Recombinant proteins were synthesized in Escherichia coli, and the antigenicity was tested using ELISA and the basophil activation test. RESULTS: In 2D-WB, nine proteins reacted with the serum IgE antibody from at least 60% of patients with WDEIA (n ≥ 25/42). ELISA revealed that alpha/beta gliadin MM1 exhibited the highest positive immunoreactivity in 23 of 26 patients who were positive for ω-5 gliadin sIgE (88%) and in 5 of 5 patients who were negative for ω-5 gliadin sIgE (100%). Alpha/beta gliadin MM1 exhibited significantly higher basophil activation in 14 patients with WDEIA when compared to 5 individuals without a wheat allergy. CONCLUSIONS: Alpha/beta gliadin MM1 sIgE exhibited the highest seropositivity, even among patients who were negative for ω-5 gliadin sIgE. The inclusion of alpha/beta gliadin MM1 in allergen-sIgE tests may improve the sensitivity for diagnosing WDEIA.

Quantitative metabolic fluxes regulated by trans-omic networks.

Cells change their metabolism in response to internal and external conditions by regulating the trans-omic network, which is a global biochemical network with multiple omic layers. Metabolic flux is a direct measure of the activity of a metabolic reaction that provides valuable information for understanding complex trans-omic networks. Over the past decades, techniques to determine metabolic fluxes, including 13C-metabolic flux analysis (13C-MFA), flux balance analysis (FBA), and kinetic modeling, have been developed. Recent studies that acquire quantitative metabolic flux and multi-omic data have greatly advanced the quantitative understanding and prediction of metabolism-centric trans-omic networks. In this review, we present an overview of 13C-MFA, FBA, and kinetic modeling as the main techniques to determine quantitative metabolic fluxes, and discuss their advantages and disadvantages. We also introduce case studies with the aim of understanding complex metabolism-centric trans-omic networks based on the determination of metabolic fluxes.

Laparoscopic Anatomic Liver Resection of the Dorsal Part of Segment 8 Using an Hepatic Vein-Guided Approach.

BACKGROUND: Laparoscopic anatomic liver resection is considered highly challenging, especially in segment 8 (S8), owing to the limited angle of the laparoscope and limited manipulation of the surgical instrument1,2. Additionally, resection is technically difficult when approaching the more peripheral branches since the Glissonean pedicle of S8 has several variations3 and is far from the hepatic hilum. The hepatic vein (HV)-guided approach involves entering from the cranial side of the liver while overcoming these difficulties with the unique view and techniques of laparoscopy4,5. We describe laparoscopic anatomic resection of the dorsal part of S8 using the HV-guided approach for hepatocellular carcinoma. METHODS: The drainage vein of segment 8 (V8), which often runs between the ventral and dorsal parts of S86,7, was exposed from the confluence of the middle HV to the periphery. The dorsal Glissonean branch of S8 (G8dor) was identified by deep dissection of the parenchyma on the right side of the V8. The right HV (RHV) was exposed toward the periphery after dissecting the G8dor. Liver parenchymal dissection was completed by connecting the demarcation line and the RHV. RESULTS: The total operation time was 319 min, estimated blood loss was 5 mL, and the patient was discharged on postoperative day 6 with no complications. CONCLUSION: Laparoscopic anatomic resection of the dorsal parts of S8 could be safely performed by exposing the HVs from their roots and using the HVs as a landmark to identify the intrahepatic Glissonean pedicles.

Intrahepatic Glissonean Approach for Laparoscopic Bisegmentectomy 7 and 8 With Root-Side Hepatic Vein Exposure.

BACKGROUND: Laparoscopic anatomic liver resections of the posterosuperior segments are technically demanding procedures.1-5 The segments are located in a deep-seated area of the liver surrounded by the ribs and the diaphragm, making forceps manipulation difficult. To overcome this limitation, an intrahepatic Glissonean approach and exposure of the hepatic veins from the root side was applied.6-10 The authors describe the technical aspects of performing a bisegmentectomy 7-8. METHODS: Liver parenchymal transection was initiated from the ventral aspect of the root of the middle hepatic vein, which often runs in the intersegmental plane, identifying the Glissonean pedicle of segment 8 (G8). After dissection of the G8, segmentectomy 8 was performed through identification of the ischemic area. After complete mobilization of the right lobe, the Glissonean pedicle of segment 7 (G7), which runs relatively near the liver surface,9, 10 was marked using ultrasonography. After division of the G7, a wide dissection between the caudate lobe and segment 7 was performed and connected to the previously dissected plane from the dorsal side of the right hepatic vein (RHV). Finally, bisegmentectomy 7-8 was performed with RHV resection because of tumor invasion. RESULTS: The operation time was 510 min, and the estimated blood loss was 150 ml. The patient was discharged on postoperative day 10 without any complications. CONCLUSIONS: Application of the intrahepatic Glissonean approach and exposure of the major hepatic veins from their roots using unique laparoscopic principles allows a safe performance of bisegmentectomy 7-8.

Outcomes and management of delayed complication after severe blunt liver injury.

BACKGROUND: The treatment of delayed complications after liver trauma such as bile leakage (BL) and hepatic artery pseudoaneurysms (HAPs) is difficult. The purpose of this study is to investigate the outcomes and management of post-traumatic BL and HAPs. METHODS: We retrospectively evaluated patients diagnosed with blunt liver injury, graded by the American Association for the Surgery of Trauma Liver Injury Scale, who were admitted to our hospital between April 2010 and December 2019. Patient characteristics and treatments were analyzed. RESULTS: A total of 176 patients with blunt liver injury were evaluated. Patients were diagnosed with grade I-II liver injury (n = 127) and with grade III-V injury (n = 49). BL was not observed in patients with grade I-II injury. Eight patients with grade III-V injury developed BL: surgical intervention was not needed for six patients with peripheral bile duct injury, but hepaticojejunostomy was needed for two patients with central bile duct injury. Out of 10 patients with HAPs, only three with grade I-II injury and one with grade III-V were treated conservatively; the rest six with grade III-V injury required transcatheter arterial embolization (TAE). All pseudoaneurysms disappeared. CONCLUSIONS: Severe blunt liver injury causing peripheral bile duct injury can be treated conservatively. In contrast, the central bile duct injury requires surgical treatment. HAPs with grade I-II injury might disappear spontaneously. HAPs with grade III-V injury should be considered TAE.

Short-term outcomes of laparoscopic versus open liver resection for hepatocellular carcinoma in older patients: a propensity score matching analysis.

BACKGROUND: The incidence of hepatocellular carcinoma (HCC) requiring surgical treatment in older patients has been continuously increasing. This study aimed to examine the safety and feasibility of performing laparoscopic liver resection (LLR) versus open liver resection (OLR) for HCC in older patients at a Japanese institution. METHODS: Between January 2010 and June 2021, 133 and 145 older patients (aged ≥ 70 years) who were diagnosed with HCC underwent LLR and OLR, respectively. Propensity score matching (PSM) analysis with covariates of baseline characteristics was performed. The intraoperative and postoperative data were evaluated in both groups. RESULTS: After PSM, 75 patients each for LLR and OLR were selected and the data compared. No significant differences in demographic characteristics, clinical data, and operative times were observed between the groups, although less than 10% of cases in each group underwent a major resection. Blood loss (OLR: 370 mL, LLR: 50 mL; P < 0.001) was lower, and the length of postoperative hospital stay (OLR: 12 days, LLR: 7 days; P < 0.001) and time to start of oral intake (OLR: 2 days, LLR: 1 day; P < 0.001) were shorter in the LLR group than in the OLR group. The incidence of complications ≥ Clavien-Dindo class IIIa was similar between the two groups. CONCLUSIONS: LLR, especially minor resections, is safely performed and feasible for selected older patients with HCC.

Identification of a radical SAM enzyme involved in the synthesis of archaeosine.

Archaeosine (G+), 7-formamidino-7-deazaguanosine, is an archaea-specific modified nucleoside found at the 15th position of tRNAs. In Euryarchaeota, 7-cyano-7-deazaguanine (preQ0)-containing tRNA (q0N-tRNA), synthesized by archaeal tRNA-guanine transglycosylase (ArcTGT), has been believed to be converted to G+-containing tRNA (G+-tRNA) by the paralog of ArcTGT, ArcS. However, we found that several euryarchaeal ArcSs have lysine transfer activity to q0N-tRNA to form q0kN-tRNA, which has a preQ0 lysine adduct as a base. Through comparative genomics and biochemical experiments, we found that ArcS forms a robust complex with a radical S-adenosylmethionine (SAM) enzyme named RaSEA. The ArcS-RaSEA complex anaerobically converted q0N-tRNA to G+-tRNA in the presence of SAM and lysine via q0kN-tRNA. We propose that ArcS and RaSEA should be considered an archaeosine synthase α-subunit (lysine transferase) and ß-subunit (q0kN-tRNA lyase), respectively.

Synthesis and activity of 3-oxo-α-ionone analogs as male attractants for the solanaceous fruit fly, Bactrocera latifrons (Diptera: Tephritidae).

A series of 3-oxygenated α-ionone analogs have been developed as highly specific male lures for the solanaceous fruit fly Bactrocera latifrons, a pest of solanaceous fruits. We compared the attractant and phagostimulant activities of analogs with or without (i) unsaturations at the 4,5- and/or 7,8-positions and (ii) oxygen moieties at the 3- and/or 9-positions of the ionone molecule. Since naturally occurring vomifoliol (V2) was found to induce a highly potent phagostimulant activity in B. latifrons males, related analogs including dehydrovomifoliol (V1), 6-hydroxy-α-ionone (U1), and 6-hydroxy-α-ionol (U2) were synthesized to evaluate their attractant and phagostimulant activities. Synthetic V1, V2, U1, and U2 exhibited low attractant activity, but their phagostimulant activity was relatively high. Optical isomers of 3-oxo-7,8-dihydro-α-ionone (P3) and V1 were prepared to examine the stereochemical specificity of attractants. (+)-(6R)-P3 and (+)-(6S)-V1 exhibited the corresponding activities, while their respective antipodal enantiomers were found entirely inactive.

How-I-do-it: laparoscopic left medial sectionectomy utilizing a cranial approach to the middle hepatic vein and Laennec's capsule.

BACKGROUND: Laparoscopic anatomic liver resection is technically demanding, given the need to safely isolate the Glissonean pedicles and expose the hepatic veins (HVs) on the liver parenchyma cut surface. Laennec's capsule is observed around the Glissonean pedicles and root of the HVs. However, its existence, particularly on the peripheral side of the HVs, remains controversial. Herein, we describe Laennec's capsule-related histopathological findings around the HVs and a safe laparoscopic left medial sectionectomy utilizing Laennec's capsule. METHODS: The extrahepatic Glissonean approach was performed by connecting Gates II and III, in accordance with Sugioka's Gate theory. Liver parenchymal transection commenced along the demarcation line, which is between the medial and lateral sections, and the G4 was dissected during transection. Subsequently, via the outer-Laennec approach, the middle hepatic vein (MHV) was exposed from the root side in cranial view, while Laennec's capsule was preserved. Parenchymal transection was completed while connecting the MHV with the demarcation line. We obtained the membrane surrounding the HVs and performed histopathological examinations. RESULTS: Six patients underwent laparoscopic left medial sectionectomy from February 2012 to November 2020. There were no cases involving complications (Clavien-Dindo classification; grade II or higher), open-surgery conversion, transfusion, or surgery-related death. The histopathological findings showed Laennec's capsule surrounding both the trunk of the major HVs and the peripheral side of the HVs. CONCLUSIONS: A cranial approach to the major HVs utilizing Laennec's capsule is a feasible and advantageous procedure for laparoscopic left medial sectionectomy. We propose that Laennec's capsule surrounds the entire length of the HVs.

Acceleration of hydrogen absorption by palladium through surface alloying with gold.

Enhancement of hydrogen (H) absorption kinetics improves the performance of hydrogen-purifying membranes and hydrogen-storage materials, which is necessary for utilizing hydrogen as a carbon-free energy carrier. Pd-Au alloys are known to show higher hydrogen solubility than pure Pd. However, the effect of Au on the hydrogen penetration from the surface into the subsurface region has not been clarified so far. Here, we investigate the hydrogen absorption at Pd-Au surface alloys on Pd(110) by means of thermal desorption spectroscopy (TDS) and hydrogen depth profiling with nuclear reaction analysis (NRA). We demonstrate that alloying the Pd(110) surface with submonolayer amounts of Au dramatically accelerates the hydrogen absorption. The degree of acceleration shows a volcano-shaped form against Au coverage. This kinetic enhancement is explained by a reduced penetration barrier mainly caused by a destabilization of chemisorbed surface hydrogen, which is supported by density-functional-theory (DFT) calculations. The destabilization of chemisorbed surface hydrogen is attributed to the change of the surface electronic states as observed by angle-resolved photoemission spectroscopy (ARPES). If generalized, these discoveries may lead to improving and controlling the hydrogen transport across the surfaces of hydrogen-absorbing materials.

Predominant accumulation of a 3-hydroxy-γ-decalactone in the male rectal gland complex of the Japanese orange fly, Bactrocera tsuneonis.

The Japanese orange fly, Bactrocera tsuneonis, infests various citrus crops. While male pheromone components accumulated in the rectal glands are well characterized for Bactrocera, but information regarding the chemical factors involved in the life cycles of B. tsuneonis remains scarce. Herein, several volatile chemicals including a γ-decalactone, (3R,4R)-3-hydroxy-4-decanolide [(3R,4R)-HD], were identified as major components, along with acetamide and spiroketals as minor components in the rectal gland complexes of male B. tsuneonis flies. The lactone (3R,4R)-HD was also identified in female rectal gland complexes. The amount of this compound in mature males was significantly higher than those observed in females and immature males. The lactone (3R,4R)-HD was detected in flies fed with sucrose only, indicating that this lactone is not derived from dietary sources during adulthood, but biosynthesized in vivo. The predominant accumulation of (3R,4R)-HD in mature males also suggests a possible role in reproductive behavior.

Multisite-specific archaeosine tRNA-guanine transglycosylase (ArcTGT) from Thermoplasma acidophilum, a thermo-acidophilic archaeon.

Archaeosine (G(+)), which is found only at position 15 in many archaeal tRNA, is formed by two steps, the replacement of the guanine base with preQ0 by archaeosine tRNA-guanine transglycosylase (ArcTGT) and the subsequent modification of preQ0 to G(+) by archaeosine synthase. However, tRNA(Leu) from Thermoplasma acidophilum, a thermo-acidophilic archaeon, exceptionally has two G(+)13 and G(+)15 modifications. In this study, we focused on the biosynthesis mechanism of G(+)13 and G(+)15 modifications in this tRNA(Leu). Purified ArcTGT from Pyrococcus horikoshii, for which the tRNA recognition mechanism and structure were previously characterized, exchanged only the G15 base in a tRNA(Leu) transcript with (14)C-guanine. In contrast, T. acidophilum cell extract exchanged both G13 and G15 bases. Because T. acidophilum ArcTGT could not be expressed as a soluble protein in Escherichia coli, we employed an expression system using another thermophilic archaeon, Thermococcus kodakarensis. The arcTGT gene in T. kodakarensis was disrupted, complemented with the T. acidophilum arcTGT gene, and tRNA(Leu) variants were expressed. Mass spectrometry analysis of purified tRNA(Leu) variants revealed the modifications of G(+)13 and G(+)15 in the wild-type tRNA(Leu). Thus, T. acidophilum ArcTGT has a multisite specificity and is responsible for the formation of both G(+)13 and G(+)15 modifications.

Correlation between the stability of tRNA tertiary structure and the catalytic efficiency of a tRNA-modifying enzyme, archaeal tRNA-guanine transglycosylase.

In many archaeal tRNAs, archaeosine is found at position 15. During archaeosine biosynthesis, archaeal tRNA-guanine transglycosylase (ArcTGT) first replaces the guanine base at position 15 with 7-cyano-7-deazaguanine (preQ0). In this study, we investigated whether modified nucleosides in tRNA substrates would affect ArcTGT incorporation of preQ0. We prepared a series of hypomodified tRNAs(Ser)(GGA) from Escherichia coli strains lacking each tRNA-modifying enzyme. Measurement of ArcTGT kinetic parameters with the various tRNAs(Ser)(GGA) as substrates showed that the Km decreased due to the lack of modified nucleosides. The tRNAs(Ser)(GGA) melting profiles resulted in experimental evidence showing that each modified nucleoside in tRNA(Ser)(GGA) enhanced tRNA stability. Furthermore, the ArcTGT K(m) strongly correlated with the melting temperature (T(m)), suggesting that the unstable tRNA containing fewer modified nucleosides served as a better ArcTGT substrate. These results show that preQ0 incorporation into tRNA by ArcTGT takes place early in the archaeal tRNA modification process.

Escherichia coli-based production of recombinant ovine angiotensinogen and its characterization as a renin substrate.

BACKGROUND: Angiotensinogen (ANG) is a macromolecular precursor of angiotensin, which regulates blood pressure and electrolyte balance. ANG is specifically cleaved by renin, an aspartic protease, to initiate the angiotensin-processing cascade. Ovine ANG (oANG) from sheep plasma has been shown to be a better substrate for human renin, and it has been used in clinical renin assays. To expand the availability of oANG, we aimed to produce milligram levels of recombinant oANG using an Escherichia coli expression system. RESULTS: When recombinant oANG was expressed from a T7 promoter in various E. coli strains at 37 °C, it accumulated in the insoluble fraction. However, by expressing oANG at 37 °C from a tac promoter, which has weaker transcriptional activity than a T7 promoter, we significantly elevated the ratio of soluble to insoluble recombinant oANG. Using a novel culturing system and auto-induction culture medium, we purified tac-expressed recombinant oANG to homogeneity, with a yield of 4.0 mg per liter of culture. Based on size-exclusion gel filtration analysis and dynamic light scattering analysis, the resulting purified oANG is a monomer in solution. The circular dichroism spectrum of E. coli-expressed recombinant oANG was similar to that of oANG expressed in CHO cells. Differential scanning fluorimetry showed that both preparations undergo a two-state transition during thermal denaturation, and the melting temperatures of recombinant oANG expressed in E. coli and CHO cells were 49.4 ± 0.16 °C and 51.6 ± 0.19 °C, respectively. The K(m) values of both oANG preparations were similar; the k(cat) value of E. coli-expressed recombinant oANG was slightly higher than that of CHO-expressed oANG. CONCLUSIONS: Recombinant oANG expressed in E. coli functions as a human renin substrate. This study presents an E. coli-based system for the rapid production of milligram quantities of a human renin substrate, which will be useful for both fundamental and clinical studies on renin and hypertension.

Advanced hepatocellular carcinoma with hepatic vein tumor thrombosis and renal dysfunction after hepatic arterial infusion chemotherapy effectively treated by liver resection with active veno-venous bypass: report of a case.

BACKGROUND: Hepatocellular carcinoma (HCC) patients with hepatic vein tumor thrombosis (HVTT) extending to the inferior vena cava (IVC) have an extremely poor prognosis. Here we report a case of HCC with HVTT and renal dysfunction after hepatic arterial infusion chemotherapy (HAIC) successfully treated by liver resection and active veno-venous bypass. CASE PRESENTATION: A 77-year-old man was diagnosed to have a large HCC with intrahepatic metastases and HVTT extending to the IVC. Due to the advanced stage, HAIC with cisplatin was performed 13 times in a period of 17 months. As a consequence of this treatment, the size of the main HCC markedly decreased, and the advanced part of the HVTT went down to the root of the right hepatic vein (RHV). However, because of renal dysfunction, HAIC with cisplatin was discontinued and right hepatectomy with patch graft venoplasty of the root of the RHV was performed. Because progression of renal dysfunction had to be avoided, veno-venous bypass was activated during IVC clamping to prevent renal venous congestion and hypotension. Histological examination showed foci of a moderately differentiated HCC with extensive fibrosis and necrosis in the main HCC. Histologically, the HVTT in the RHV showed massive necrosis and tightly adhered to the vascular wall of the RHV. The postoperative function of the remnant liver was good, and no further deterioration of renal function was detected. The patient did not show signs of recurrence 15 month after surgery. CONCLUSION: In the present case, HAIC using cisplatin in combination with hepatic resection and patch graft venoplasty of the IVC provided a good long-term outcome with no HCC recurrence. Renal function was preserved by using active veno-venous bypass during IVC clamping to prevent renal venous congestion and hypotension.

FastPros: screening of reaction knockout strategies for metabolic engineering.

MOTIVATION: Although constraint-based flux analysis of knockout strains has facilitated the production of desirable metabolites in microbes, current screening methods have placed a limitation on the number knockouts that can be simultaneously analyzed. RESULTS: Here, we propose a novel screening method named FastPros. In this method, the potential of a given reaction knockout for production of a specific metabolite is evaluated by shadow pricing of the constraint in the flux balance analysis, which generates a screening score to obtain candidate knockout sets. To evaluate the performance of FastPros, we screened knockout sets to produce each metabolite in the entire Escherichia coli metabolic network. We found that 75% of these metabolites could be produced under biomass maximization conditions by adding up to 25 reaction knockouts. Furthermore, we demonstrated that using FastPros in tandem with another screening method, OptKnock, could further improve target metabolite productivity. AVAILABILITY AND IMPLEMENTATION: Source code is freely available at http://www-shimizu.ist.osaka-u.ac.jp/shimizu_lab/FastPros/, implemented in MATLAB and COBRA toolbox.

A vector library for silencing central carbon metabolism genes with antisense RNAs in Escherichia coli.

We describe here the construction of a series of 71 vectors to silence central carbon metabolism genes in Escherichia coli. The vectors inducibly express antisense RNAs called paired-terminus antisense RNAs, which have a higher silencing efficacy than ordinary antisense RNAs. By measuring mRNA amounts, measuring activities of target proteins, or observing specific phenotypes, it was confirmed that all the vectors were able to silence the expression of target genes efficiently. Using this vector set, each of the central carbon metabolism genes was silenced individually, and the accumulation of metabolites was investigated. We were able to obtain accurate information on ways to increase the production of pyruvate, an industrially valuable compound, from the silencing results. Furthermore, the experimental results of pyruvate accumulation were compared to in silico predictions, and both sets of results were consistent. Compared to the gene disruption approach, the silencing approach has an advantage in that any E. coli strain can be used and multiple gene silencing is easily possible in any combination.

Increased 3-hydroxypropionic acid production from glycerol, by modification of central metabolism in Escherichia coli.

BACKGROUND: 3-hydroxypropionic acid (3HP) is an important chemical precursor for the production of bioplastics. Microbial production of 3HP from glycerol has previously been developed through the optimization of culture conditions and the 3HP biosynthesis pathway. In this study, a novel strategy for improving 3HP production in Escherichia coli was investigated by the modification of central metabolism based on a genome-scale metabolic model and experimental validation. RESULTS: Metabolic simulation identified the double knockout of tpiA and zwf as a candidate for improving 3HP production. A 3HP-producing strain was constructed by the expression of glycerol dehydratase and aldehyde dehydrogenase. The double knockout of tpiA and zwf increased the percentage carbon-molar yield (C-mol%) of 3HP on consumed glycerol 4.4-fold (20.1 ± 9.2 C-mol%), compared to the parental strain. Increased extracellular methylglyoxal concentrations in the ΔtpiA Δzwf strain indicated that glycerol catabolism was occurring through the methylglyoxal pathway, which converts dihydroxyacetone phosphate to pyruvate, as predicted by the metabolic model. Since the ΔtpiA Δzwf strain produced abundant 1,3-propanediol as a major byproduct (37.7 ± 13.2 C-mol%), yqhD, which encodes an enzyme involved in the production of 1,3-propanediol, was disrupted in the ΔtpiA Δzwf strain. The 3HP yield of the ΔtpiA Δzwf ΔyqhD strain (33.9 ± 1.2 C-mol%) was increased 1.7-fold further compared to the ΔtpiA Δzwf strain and by 7.4-fold compared to the parental strain. CONCLUSION: This study successfully increased 3HP production by 7.4-fold in the ΔtpiA Δzwf ΔyqhD E. coli strain by the modification of the central metabolism, based on metabolic simulation and experimental validation of engineered strains.

Novel insight into the hydrogen absorption mechanism at the Pd(110) surface.

The microscopic mechanism of low-temperature (80 K < T < 160 K) hydrogen (H) ingress into the H2 (<2.66 × 10(-3) Pa) exposed Pd(110) surface is explored by H depth profiling with (15)N nuclear reaction analysis (NRA) and thermal desorption spectroscopy (TDS) with isotope (H, D) labeled surface hydrogen. NRA and TDS reveal two types of absorbed hydrogen states of distinctly different depth distributions. Between 80 K and ∼145 K a near-surface hydride phase evolving as the TDS α1 feature at 160 K forms, which initially extends only several nanometers into depth. On the other hand, a bulk-absorbed hydrogen state develops between 80 K and ∼160 K which gives rise to a characteristic α3 TDS feature above 190 K. These two absorbed states are populated at spatially separated surface entrance channels. The near-surface hydride is populated through rapid penetration at minority sites (presumably defects) while the bulk-absorbed state forms at regular terraces with much lower probability per site. In both cases, absorption of gas phase hydrogen transfers pre-adsorbed hydrogen atoms below the surface and replaces them at the chemisorption sites by post-dosed hydrogen in a process that requires much less activation energy (<100 meV) than monatomic diffusion of chemisorbed H atoms into subsurface sites. This small energy barrier suggests that the rate-determining step of the absorption process is either H2 dissociation on the H-saturated Pd surface or a concerted penetration mechanism, where excess H atoms weakly bound to energetically less favorable adsorption sites stabilize themselves in the chemisorption wells while pre-chemisorbed H atoms simultaneously transit into the subsurface. The peculiarity of absorption at regular Pd(110) terraces in comparison to Pd(111) and Pd(100) is discussed.