Aldehyde Reductase Activity of Carboxylic Acid Reductases

Carboxylic acid reductase enzymes (CARs) are well known for the reduction of a wide range of carboxylic acids to the respective aldehydes. One of the essential CAR domains - the reductase domain (R-domain) - was recently shown to catalyze the standalone reduction of carbonyls, including aldehydes, which are typically considered to be the final product of carboxylic acid reduction by CAR. We discovered that the respective full-length CARs were equally able to reduce aldehydes. Herein we aimed to shed light on the impact of this activity on aldehyde production and acid reduction in general. Our data explains previously inexplicable results and a new CAR from Mycolicibacterium wolinskyi is presented.

Enzymatic reactions towards aldehydes: An overview

Many aldehydes are volatile compounds with distinct and characteristic olfactory properties. The aldehydic functional group is reactive and, as such, an invaluable chemical multi-tool to make all sorts of products. Owing to the reactivity, the selective synthesis of aldehydic is a challenging task. Nature has evolved a number of enzymatic reactions to produce aldehydes, and this review provides an overview of aldehyde-forming reactions in biological systems and beyond. Whereas some of these biotransformations are still in their infancy in terms of synthetic applicability, others are developed to an extent that allows their implementation as industrial biocatalysts.

Antiarrhythmic Drug Dosing in Children-Review of the Literature

Antiarrhythmic drugs represent a mainstay of pediatric arrhythmia treatment. However, official guidelines and consensus documents on this topic remain scarce. There are rather uniform recommendations for some medications (including adenosine, amiodarone, and esmolol), while there are only very broad dosage recommendations for others (such as sotalol or digoxin). To prevent potential uncertainties and even mistakes with regard to dosing, we summarized the published dosage recommendations for antiarrhythmic drugs in children. Because of the wide variations in availability, regulatory approval, and experience, we encourage centers to develop their own specific protocols for pediatric antiarrhythmic drug therapy.

Precision of time-resolved near-infrared spectroscopy-based measurements of cerebral oxygenation in preterm infants

Significance: Time-resolved near-infrared spectroscopy (t-NIRS) is a new technology; at the moment, data on its precision in preterm infants are rare. Aim: Therefore, the aim of this study was to analyze the precision of t-NIRS-based measurements of the cerebral oxygenation in preterm infants. Approach: In 70 neonates [age: 4.7 ± 2.0 days, sex (f/m): 33/37], cerebral oxygenation ( t - rSO 2 ) was measured with an optode placed over the left frontotemporal lobe on the head, measurement duration was 1 min, and a reapplication was done for four further times (five applications). Results: Overall mean for t - rSO 2 values was 62.2 % ± 4.1 % . We found a within-patient variation for t - rSO 2 of 2.6%. Furthermore, 95% of all observed values were within a range of ± 5 % from the mean when looking on several reapplications and ± 2 % when looking within one application. Most of the variation in t - rSO 2 (60.4%) contributed to differences between patients. The remaining 39.6% of the variation was due to measurement errors and real changes of the measured signal within the neonates. Conclusions: Since within-patient variation of t - rSO 2 measures were below a clinical meaningful threshold of 5%, the measurement can be denoted as precise.

Thiols Act as Methyl Traps in the Biocatalytic Demethylation of Guaiacol Derivatives

Demethylating methyl phenyl ethers is challenging, especially when the products are catechol derivatives prone to follow-up reactions. For biocatalytic demethylation, monooxygenases have previously been described requiring molecular oxygen which may cause oxidative side reactions. Here we show that such compounds can be demethylated anaerobically by using cobalamin-dependent methyltransferases exploiting thiols like ethyl 3-mercaptopropionate as a methyl trap. Using just two equivalents of this reagent, a broad spectrum of substituted guaiacol derivatives were demethylated, with conversions mostly above 90 %. This strategy was used to prepare the highly valuable antioxidant hydroxytyrosol on a one-gram scale in 97 % isolated yield.

Thiols Act as Methyl Traps in the Biocatalytic Demethylation of Guaiacol Derivatives

Demethylating methyl phenyl ethers is challenging, especially when the products are catechol derivatives prone to follow-up reactions. For biocatalytic demethylation, monooxygenases have previously been described requiring molecular oxygen which may cause oxidative side reactions. Here we show that such compounds can be demethylated anaerobically by using cobalamin-dependent methyltransferases exploiting thiols like ethyl 3-mercaptopropionate as a methyl trap. Using just two equivalents of this reagent, a broad spectrum of substituted guaiacol derivatives were demethylated, with conversions mostly above 90 %. This strategy was used to prepare the highly valuable antioxidant hydroxytyrosol on a one-gram scale in 97 % isolated yield.

Effect of Particle Wettability and Particle Concentration on the Enzymatic Dehydration of n-Octanaloxime in Pickering Emulsions

Pickering emulsion systems have emerged as platforms for the synthesis of organic molecules in biphasic biocatalysis. Herein, the catalytic performance was evaluated for biotransformation using whole cells exemplified for the dehydration of n-octanaloxime to n-octanenitrile catalysed by an aldoxime dehydratase (OxdB) overexpressed in E. coli. This study was carried out in Pickering emulsions stabilised solely with silica particles of different hydrophobicity. We correlate, for the first time, the properties of the emulsions with the conversion of the reaction, thus gaining an insight into the impact of the particle wettability and particle concentration. When comparing two emulsions of different type with similar stability and droplet diameter, the oil-in-water (o/w) system displayed a higher conversion than the water-in-oil (w/o) system, despite the conversion in both cases being higher than that in a "classic" two-phase system. Furthermore, an increase in particle concentration prior to emulsification resulted in an increase of the interfacial area and hence a higher conversion.

Regioselectivity of Cobalamin-Dependent Methyltransferase Can Be Tuned by Reaction Conditions and Substrate

Regioselective reactions represent a significant challenge for organic chemistry. Here the regioselective methylation of a single hydroxy group of 4-substituted catechols was investigated employing the cobalamin-dependent methyltransferase from Desulfitobacterium hafniense. Catechols substituted in position four were methylated either in meta- or para-position to the substituent depending whether the substituent was polar or apolar. While the biocatalytic cobalamin dependent methylation was meta-selective with 4-substituted catechols bearing hydrophilic groups, it was para-selective for hydrophobic substituents. Furthermore, the presence of water miscible co-solvents had a clear improving influence, whereby THF turned out to enable the formation of a single regioisomer in selected cases. Finally, it was found that also the pH led to an enhancement of regioselectivity for the cases investigated.

Catalytic and enantioselective oxa-Piancatelli reaction using a chiral vanadium complex

An enantioselective oxa-Piancatelli reaction was established for the first time using a chiral vanadium(v) catalyst. The dual Brønsted and Lewis acid properties of the vanadium catalyst afforded 4-hydroxycyclopent-2-enone derivatives in up to 90% yields and with 93 : 7 enantiomeric ratios, as well as >20 : 1 diastereomeric ratios.

An Asymmetric Organocatalytic Aldol Reaction of a Hydrophobic Aldehyde in Aqueous Medium Running in Flow Mode

Reaction conditions have been identified to conduct a one-pot asymmetric organocatalytic aldol reaction with a hydrophobic substrate in aqueous medium via a process running in flow mode. By employing a mixture of water and 2-propanol, a hydrophobic aldehyde and 3.6 mol% of an organocatalyst, this microreactor process affords the desired aldol adduct with a conversion of 74% and an enantioselectivity of 89% after a reaction time of 60 minutes.

Cerebral Oxygenation in Neonates Immediately after Cesarean Section and Mode of Maternal Anesthesia

BACKGROUND

Cerebral regional oxygen saturation (crSO2) during immediate transition and resuscitation immediately after birth is of increasing interest.

OBJECTIVES

The aim of the present study was to assess whether the type of maternal anesthesia during cesarean section (CS; general anesthesia vs. spinal anesthesia) has an influence on cerebral oxygenation during immediate neonatal transition after birth.

METHODS

Secondary outcome parameters of prospective observational studies were analyzed. Neonates born by CS from November 2009 to September 2016 at the Medical University of Graz (Austria) were eligible. Term and preterm neonates were included, provided that: (1) crSO2 was measured by near-infrared spectroscopy, and (2) peripheral arterial oxygen saturation (SpO2) and heart rate (HR) were measured by pulse oximetry during the first 15 min after birth. Administration of supplemental oxygen was recorded and cerebral fractional tissue oxygen extraction (cFTOE) was calculated out of crSO2 and SpO2. For comparison, term and preterm neonates with maternal general anesthesia were matched to neonates with maternal spinal anesthesia during CS.

RESULTS

Out of 760 eligible neonates, 64 term (38.8 ± 0.9 weeks of gestation; 32 neonates in each group) and 54 preterm neonates (32.0 ± 2.9 weeks of gestation; 27 neonates in each group) were included. In term neonates, maternal general anesthesia was associated with lower initial SpO2, HR values, and Apgar scores. The fraction of inspired oxygen (FiO2) was statistically significantly higher in the general anesthesia group. Nevertheless, crSO2 and cFTOE did not differ statistically significantly between the groups. In preterm neonates there were no statistically significant differences in SpO2, HR, crSO2, and cFTOE between the general and spinal anesthesia groups. Apgar scores at 1 min were statistically significantly lower and FiO2 was statistically significantly higher in the general anesthesia group.

CONCLUSION

Cerebral tissue oxygenation in neonates during immediate transition after birth was similar after maternal general and spinal anesthesia during CS, despite differences in SpO2, HR, and supplemental oxygen in term neonates and differences in supplemental oxygen in preterm neonates.

Chiral Dinuclear Vanadium Complex-Mediated Oxidative Coupling of Resorcinols

A method for the highly regio- and enantioselective oxidative coupling of resorcinols has been established by using dibrominated dinuclear vanadium(V) catalyst 1c under air. When resorcinols bearing an aryl substituent were applied as substrates to the coupling, axially chiral biresorcinols were obtained as single regioisomers in high yield with up to 98% ee.

Catch-up validation study of an in vitro skin irritation test method based on an open source reconstructed epidermis (phase II)

To replace the Draize skin irritation assay (OECD guideline 404) several test methods based on reconstructed human epidermis (RHE) have been developed and were adopted in the OECD test guideline 439. However, all validated test methods in the guideline are linked to RHE provided by only three companies. Thus, the availability of these test models is dependent on the commercial interest of the producer. To overcome this limitation and thus to increase the accessibility of in vitro skin irritation testing, an open source reconstructed epidermis (OS-REp) was introduced. To demonstrate the capacity of the OS-REp in regulatory risk assessment, a catch-up validation study was performed. The participating laboratories used in-house generated OS-REp to assess the set of 20 reference substances according to the performance standards amending the OECD test guideline 439. Testing was performed under blinded conditions. The within-laboratory reproducibility of 87% and the inter-laboratory reproducibility of 85% prove a high reliability of irritancy testing using the OS-REp protocol. In addition, the prediction capacity was with an accuracy of 80% comparable to previous published RHE based test protocols. Taken together the results indicate that the OS-REp test method can be used as a standalone alternative skin irritation test replacing the OECD test guideline 404.

The role of regulatory T cell (Treg) subsets in gestational diabetes mellitus

Physiological changes during normal pregnancy are characterized by an inflammatory immune response and insulin resistance. Therefore, we hypothesize that gestational diabetes mellitus (GDM) may be caused by an inappropriate adaption of the maternal immune system to pregnancy. In this study we examined the role of regulatory T cell (Treg) differentiation for the development of GDM during pregnancy. We used six-colour flow cytometric analysis to demonstrate that the total CD4(+) CD127(low+/-) CD25(+) forkhead box protein 3 (FoxP3(+)) T(reg) pool consists of four different T(reg) subsets: naive CD45RA(+) T(regs), HLA-DR(-) CD45RA(-) memory T(regs) (DR(-) T(regs)) and the highly differentiated and activated HLA-DR(low+) CD45RA(-) and HLA-DR(high+) CD45RA(-) memory T(regs) (DR(low+) and DR(high+) T(regs)). Compared to healthy pregnancies, the percentage of CD4(+) CD127(low+/-) CD25(+) FoxP3(+) T(regs) within the total CD4(+) T helper cell pool was not different in patients affected by GDM. However, the suppressive activity of the total CD4(+) CD127(low+/-) CD25(+) T(reg) pool was significantly reduced in GDM patients. The composition of the total T(reg) pool changed in the way that its percentage of naive CD45RA(+) T(regs) was decreased significantly in both patients with dietary-adjusted GDM and patients with insulin-dependent GDM. In contrast, the percentage of DR(-) -memory T(regs) was increased significantly in patients with dietary-adjusted GDM, while the percentage of DR(low+) and DR(high+) memory T(regs) was increased significantly in patients with insulin-dependent GDM. Hence, our findings propose that alterations in homeostatic parameters related to the development and function of naive and memory T(regs) may cause the reduction of the suppressive capacity of the total T(reg) pool in GDM patients. However, as this is an exploratory analysis, the results are only suggestive and require further validation.

Determination of optical parameters for light penetration in particulate materials and soils with diffuse reflectance (DR) spectroscopy

The results of our investigations of particulate materials (aluminium oxide, quartz sand) and "real world" soils (a brown sand and a dark brown soil) using diffuse reflectance (DR) spectroscopy are presented. The findings are discussed within the framework of Kubelka-Munk (KM) theory as a simplified description of light propagation in highly turbid media. The relation between the KM and the Lambert-Beer (LB) treatment is outlined. The KM parameters determined were the scattering and absorption coefficients (S and K, respectively), and the light penetration depths, dp(KM). It was found that in the UV/VIS spectral range the scattering coefficients of the materials investigated vary by ca. one order of magnitude (S = 6-> 100 cm-1), whereas the absorption coefficients change by more than three orders of magnitude (K = < 1-> 1500 cm-1). The different absorption and scattering properties of the materials lead to strong variations in light penetration depths from the micron into the mm regime [dp(KM) = < 20-> 3500 microns].

Combination of laser-induced fluorescence and diffuse-reflectance spectroscopy for the in situ analysis of diesel-fuel-contaminated soils

Results of our laser-induced fluorescence (LIF) and diffuse-reflectance investigations of quartz sand and different soils spiked with Diesel fuel are reported. The LIF calibration functions, which were found to be significantly different for the various matrices, and the limits of detection were determined. For excitation at lambda(ex) = 266 nm, the limits of detection obtained ranged from 7 parts in 10(6) for quartz sand to approximately 200 parts in 10(6) for dark sand with organic matter and for dark peat. Furthermore, the diffuse-reflectance spectra of the matrices in the ultraviolet-near-IR range were determined. An attempt to correlate the slopes of the LIF calibration functions with the reflectances of the matrices is presented. The obtained normalized calibration functions are well suited to take into account relevant optical soil parameters and to reduce the variability of the LIF calibration behavior significantly.