Hydrogen Bonding Shuts Down Tunneling in Hydroxycarbenes: A Gas-Phase Study by Tandem-Mass Spectrometry, Infrared Ion Spectroscopy, and Theory

Hydroxycarbenes can be generated and structurally characterized in the gas phase by collision-induced decarboxylation of α-keto carboxylic acids, followed by infrared ion spectroscopy. Using this approach, we have shown earlier that quantum-mechanical hydrogen tunneling (QMHT) accounts for the isomerization of a charge-tagged phenylhydroxycarbene to the corresponding aldehyde in the gas phase and above room temperature. Herein, we report the results of our current study on aliphatic trialkylammonio-tagged systems. Quite unexpectedly, the flexible 3-(trimethylammonio)propylhydroxycarbene turned out to be stable─no H-shift to either aldehyde or enol occurred. As supported by density functional theory calculations, this novel QMHT inhibition is due to intramolecular H-bonding of a mildly acidic α-ammonio C-H bonds to the hydroxyl carbene's C-atom (C:···H-C). To further support this hypothesis, (4-quinuclidinyl)hydroxycarbenes were synthesized, whose rigid structure prevents this intramolecular H-bonding. The latter hydroxycarbenes underwent "regular" QMHT to the aldehyde at rates comparable to, e.g., methylhydroxycarbene studied by Schreiner et al. While QMHT has been shown for a number of biological H-shift processes, its inhibition by H-bonding disclosed here may serve for the stabilization of highly reactive intermediates such as carbenes, even as a mechanism for biasing intrinsic selectivity patterns.

Unidirectional Double- and Triple-Hydrogen Rearrangement Reactions Probed by Infrared Ion Spectroscopy

Unidirectional double-hydrogen (2H) and triple-hydrogen (3H) rearrangement reactions occur upon electron-ionization-induced fragmentation of trans-2-(4-N,N-dimethylaminobenzyl)-1-indanol (1), trans-2-(4-methoxybenzyl)-1-indanol (2), 4-(4-N,N-dimethylaminophenyl)-2-butanol (3), and related compounds, as reported some 35 years ago (Kuck, D.; Filges, U. Org. Mass Spectrom. 1988, 23, 643-653). These unusual intramolecular redox processes were found to dominate the mass spectra of long-lived, metastable ions. The present report provides independent evidence for the structures of the product ions formed by the 2H and 3H rearrangement in an ion trap instrument. The radical cations 1^•+ and 3^•+ as well as ionized 1-(4-N,N-dimethylaminophenyl)-5-(4-methoxyphenyl)-3-pentanol, 5^•+, were generated by electrospray ionization from anhydrous acetonitrile solutions. The 2H and 3H fragment ions were obtained by collision-induced dissociation and characterized by IR ion spectroscopy and density functional theory calculations. Comparison of the experimental and calculated infrared ion spectra enabled the identification of the 2H rearrangement product ion, C₉H₁₄N⁺ (m/z 136), as an N,N-dimethyl-para-toluidinium ion bearing the extra proton ortho to the amino group, a tautomer which was calculated to be 31 kJ/mol less stable than the corresponding N-protonated form. The 3H rearrangement product ion, C₈H₁₃N^•+ (m/z 123), formerly assumed to be a distonic ammonium ion bearing a cyclohexadienyl radical, was now identified as a conventional radical cation, ionized N,N-dimethyl-2,3-dihydro-para-toluidine. Thus, the 3H rearrangement represents an intramolecular transfer hydrogenation between a secondary alcohol and an ionized aromatic ring. Based on these structural assignments, more detailed mechanisms for the unidirectional 2H and 3H rearrangement reactions are proposed.

Impact of positive resection margins (R1) on long-term survival of patients with advanced diffuse type gastric cancer

Objective

Gastric cancer (GC) is a leading cause of cancer-related mortality worldwide. Diffuse type GC have a much worse prognosis compared to intestinal type GC. There is an ongoing debate whether microscopic involvement of the proximal margin (R1 resection) influences overall survival (OS) in advanced gastric cancer.

The aim of this study was to assess OS in patients with diffuse gastric cancers and positive lymph node involvement who underwent oncological gastrectomy with R0 and R1 resections.

Methods

All consecutive patients from two tertiary centers operated with curative intent for diffuse gastric cancer between January 2005 and December 2018 were analyzed. Patients with R2 resections or missing data were excluded. Extracted data included demographics, major comorbidities, ASA score, neo-adjuvant treatment, pre- and postoperative staging (TNM 8th edition), postoperative complication with grading according to Clavien classification, survival data and pattern of recurrence. Lymph node involvement was based on pathology.

Kaplan-Meier curves with log-rank test for comparison were used to evaluate survival between groups.

Results

A total of 94 patients with diffuse gastric cancer were included. Two patients were excluded because of R2 resection and missing data regarding pathology, leaving a cohort of 92 patients (48 male, 44 female, median age 62 years). Sixty-four patients were lymph node positive (pN+); 48 patients (75%) with R0 resection and 16 patients (25%) with R1 resection. No difference in terms of preoperative data and intraoperative characteristics was found between R0 and R1 groups. Median OS was better in the R0 group (27 months, 95% CI 17–37) compared to R1 group (7 months, 95% CI 3–11, p<0.001). Similar results were found with disease-free survival (DSF) (25 vs. 6 months, p=0.002).

On multivariable analysis, T stage and resection margin (R status) were independent factors predicting OS (T stage: HR 4.5, p<0.001, R status: HR 4.2, p<0.001) and DFS (T stage: HR 2.9, p=0.004, R status: HR 3.5, p=0.001) in the cohort of patients with lymph node involvement.

Conclusion

The present series confirmed that patients with negative surgical margins have better OS compared to patients with positive margins in case of locally advanced diffuse GC. Therefore, R0 resections should be the goal of oncological gastrectomies.

Experts' Perceived Patient Burden and Outcomes of Knee-ankle-foot-orthoses (Kafos) Vs. Microprocessor-stance-and-swing-phase-controlled-knee-ankle-foot Orthoses (Mp-sscos)

BACKGROUND

Patients with neuromuscular knee-instability assisted with orthotic devices experience problems including pain, falls, mobility issues and limited engagement in daily activities.

OBJECTIVES

The aim of this study was to analyse current real-life burden, needs and orthotic device outcomes in patients in need for advanced orthotic knee-ankle-foot-orthoses (KAFOs).

METHODOLOGY

An observer-based semi-structured telephone interview with orthotic care experts in Germany was applied. Interviews were transcribed and content-analysed. Quantitative questions were analysed descriptively.

FINDINGS

Clinical experts from eight centres which delivered an average of 49.9 KAFOs per year and 13.3 microprocessor-stance-and-swing-phase-controlled-knee-ankle-foot orthoses (MP-SSCOs) since product availability participated. Reported underlying conditions comprised incomplete paraplegia (18%), peripheral nerve lesions (20%), poliomyelitis (41%), post-traumatic lesions (8%) and other disorders (13%). The leading observed patient burdens were "restriction of mobility" (n=6), followed by "emotional strain" (n=5) and "impaired gait pattern" (n=4). Corresponding results for potential patient benefits were seen in "improved quality-of-life" (n=8) as well as "improved gait pattern" (n=8) followed by "high reliability of the orthosis" (n=7). In total, experts reported falls occurring in 71.5% of patients at a combined annual frequency of 7.0 fall events per year when using KAFOs or stance control orthoses (SCOs). In contrast, falls were observed in only 7.2 % of MPSSCO users.

CONCLUSION

Advanced orthotic technology might contribute to better quality of life of patients, improved gait pattern and perceived reliability of orthosis. In terms of safety a substantial decrease in frequency of falls was observed when comparing KAFO and MP-SSCO users.

Spigelian hernia: current approaches to surgical treatment-a review

BACKGROUND

Spigelian hernias (SpH) belong to the group of eponymous abdominal wall hernias. Major reasons for diagnostic difficulties are its low incidence reaching maximum 2% of abdominal wall hernias, a specific anatomical localization with intact external oblique aponeurosis covering the hernia sac and non-constant clinical presentation.

METHODS

A literature review was completed to summarize current knowledge on surgical treatment options and results.

RESULTS

SpH presents a high incarceration risk and therefore should be operated upon even if the patient is asymptomatic. Both laparoscopic and open repair approaches are validated by current guidelines with lesser postoperative complications and shorter hospital stay in favour of minimally invasive surgery, regardless of the technique used. Overall recurrence rate is very low.

CONCLUSION

All diagnosed SpH should be planned for elective operation to prevent strangulated hernia and, therefore emergency surgery. Both open and laparoscopic SpH treatment can be safely performed, depending on surgeon's experience. In most cases, a mesh repair is generally advised.

Multimodal management of gastroesophageal junction adenocarcinoma: Which type of neoadjuvant treatment?

Objective

The current treatment for locally advanced gastroesophageal junction (GEJ) adenocarcinoma consists of neoadjuvant treatment (NAT) followed by surgery. Preoperative chemotherapy (CT) and radio-chemotherapy (RCT) are both valid options, but comparative data for their efficacy remain scarce. This study aimed to assess the efficacy of RCT and CT to achieve a complete pathologic response (CPR) for locally advanced GEJ adenocarcinoma. Secondary endpoints were R0 resection rates, postoperative complications, long-term survival and recurrence.

Methods

All consecutive patients with locally advanced GEJ adenocarcinoma treated with CT or RCT and oncologic resection from 2009 to 2018 were included. A CPR was defined with the Mandard tumor regression score. Standard statistical tests were used as appropriate. Overall and disease-free survival were compared with the Kaplan Meier method and log-rank test. Multivariate analysis was performed to define independent predictors of CPR, and long-term survival.

Results

Among the 94 patients (84%male, median age 62 years [IQR 9.7]), 67 (71.3%) received preoperative RCT and 27 (28.7%) CT. Patient’s characteristics and pretreatment tumor stages were comparable. Surgical approach was thoracoabdominal Lewis resection in 95.5% RCT and 81.5% CT patients (P = 0.085). CPR was more frequent in the RCT than the CT group (13.4% vs 7.4%, P = 0.009), but R0 resection rates were similar (72.1% vs 66.7%, P = 0.628). There was a trend to higher ypN0 stage in the RCT group (55.2% vs 33.3%; P = 0.057). Postoperatively, RCT patients presented more cardiovascular complications (35.8% vs 11.1%; P = 0.017), although overall morbidity was similar (68.6% vs 62.9%, P = 0.988). 5-year overall survival was comparable (61.1% RCT vs 75.7% CT, P = 0.259), as was 5-year disease-free survival (33.5% RCT vs 22.8% CT, P = 0.763). Isolated loco-regional recurrence occurred in 2.9% RCT vs 3.7% CT patients (P = 0.976). NAT type was not an independent predictor for complete pathologic response nor long-term survival in the multivariate analysis. Median follow-up was 30 months [95%CI 21.3-38.8] for all patients.

Conclusion

Patients with locally advanced GEJ adenocarcinoma demonstrated higher rates of CPR after RCT than CT, and a trend to a better lymph node sterilization, although this did not translate in a significant survival benefit or decreased recurrence rate.

Preoperative hiatal hernia in oesophageal adenocarcinoma: An impact on patient outcomes?

Objective

Uncontrolled gastroesophageal reflux and the often-associated hiatal hernia (HH) are frequently encountered in oesophageal adenocarcinoma patients. Previous data suggest unfavourable long-term oncologic outcomes in the presence of a HH, but the evidence remains scarce. The aim of this study was to assess the potential impact of preoperative HH on histologic response after neoadjuvant treatment (NAT), as well as on overall and disease-free survival.

Methods

All patients operated for an adenocarcinoma of the oesophagus or gastro-oesophageal junction (GOJ) between 2012-2018 were assessed. Baseline endoscopy and CT-scan images were retrospectively reviewed to identify the presence of a clinically significant HH (≥3cm). Response to neoadjuvant treatment (Mandard TRG grade), postoperative outcomes and survival were compared between HH and non-HH patients. Categorical variables were compared with the x2 or Fisher’s test, whereas continuous ones with the Mann-Whitney-U test. Survival analyses were performed with the Kaplan-Meier method and log-rank test.

Results

Overall, 101 patients were included (84.1% male, median age 63 years); among them, 33 (32.7%) had a HH ≥ 3cm at diagnosis of oesophageal cancer. There were no significant baseline differences in demographics and tumour stages between the two groups. NAT was used in 80.9% of non-HH versus 81.8% HH patients (P = 0.910), most often chemoradiation (57.3% in non-HH versus 63.6% in HH patients, P = 0.423). Surgical approach and postoperative complication rates were similar in all patients. Good response to NAT (TRG 1-2) was observed in 32.3% of non-HH, versus 33.3% of HH patients (P = 0.297), whereas R0 resection was achieved in 94.1% vs 90.9% of patients respectively (P = 0.551). Overall survival was comparable between HH (median 28 mo, 95%CI 22-NA) and non-HH patients (median 41mo, 95% CI 29-NA) (P = 0.605). Disease-free survival was also similar (median 18 mo, 95%CI 12-NA for HH, vs 34mo, 95%CI 14-NA for non-HH patients, P = 0.283), although HH patients experienced higher rates of distant (51.6% vs 29.2% for non-HH, P = 0.033), but not locoregional recurrence.

Conclusion

A clinically significant HH is encountered in almost a third of patients with oesophageal adenocarcinoma. However, in our study, it was not associated with a worse response to NAT, nor did it lead to a worse overall and disease-free survival.

External validation of three nomograms predicting survival using an international cohort of patients with resected pancreatic head ductal adenocarcinoma

Objective

Lymph node ratio (LNR, positive lymph nodes/collected lymph nodes during surgery) was identified as an important prognostic factor of survival in resected pancreatic cancer. Several nomograms based on LNR were recently proposed to predict survival after pancreatoduodenectomy (PD). The present study aimed to externally validate 3 published nomograms using an international cohort.

Methods

Consecutive patients with ductal adenocarcinoma of the pancreatic head who underwent PD without neoadjuvant treatment from 6 tertiary centers in Europe and the USA were retrospectively collected from 2000 to 2017. Patients with metastases at diagnosis, R2 resection, missing data regarding LNR, and who died within 90 postoperative days were excluded. The 3 selected nomograms were the updated Amsterdam nomogram (including LNR, adjuvant therapy, margin status, and tumor grade), the nomogram by Pu et al. (including LNR, age, tumor grade, and T stage) and the nomogram by Li et al. (including LNR, age, tumor location, grade, size, and TNM stage). Overall survivals (OS) were calculated using Kaplan-Meier method. For the validation, calibration (Hosmer-Lemeshow test), discrimination capacity (ROC curves for 3-year OS), and clinical utility (sensitivity and specificity at the value of Youden index) were assessed.

Results

After exclusion of 95 patients with metastases, R2 resection, and who died within 90 postoperative days, 1167 patients were included. Median OS of the entire cohort was 23 months (95% confidence interval: 21-24).

For the 3 nomograms, Kaplan-Meier curves showed significant diminution of OS with increasing scores (p < 0.01 for the 3 nomograms). All nomograms showed good calibration (non significant Hosmer-Lemeshow goodness-of-fit tests). For the updated Amsterdam nomogram, the area under the ROC curve (AUROC) for 3-year OS was 0.66. Sensitivity and specificity were 73% and 50%. Regarding the nomogram by Pu et al., the AUROC was 0.67. Sensitivity and specificity were 65% and 60%. For the nomogram by Li et al., the AUROC was 0.67, while sensitivity and specificity were 56% and 71%.

Conclusion

The 3 selected nomograms were validated using an external international cohort and displayed interesting and comparable predictive values. Those nomograms may be used in clinical practice to estimate survival after PD for ductal adenocarcinoma.

Breslow Intermediates (Amino Enols) and Their Keto Tautomers: First Gas-Phase Characterization by IR Ion Spectroscopy

Breslow intermediates (BIs) are the crucial nucleophilic amino enol intermediates formed from electrophilic aldehydes in the course of N-heterocyclic carbene (NHC)-catalyzed umpolung reactions. Both in organocatalytic and enzymatic umpolung, the question whether the Breslow intermediate exists as the nucleophilic enol or in the form of its electrophilic keto tautomer is of utmost importance for its reactivity and function. Herein, the preparation of charge-tagged Breslow intermediates/keto tautomers derived from three different types of NHCs (imidazolidin-2-ylidenes, 1,2,4-triazolin-5-ylidenes, thiazolin-2-ylidenes) and aldehydes is reported. An ammonium charge tag is introduced through the aldehyde unit or the NHC. ESI-MS IR ion spectroscopy allowed the unambiguous conclusion that in the gas phase, the imidazolidin-2-ylidene-derived BI indeed exists as a diamino enol, while both 1,2,4-triazolin-5-ylidenes and thiazolin-2-ylidenes give the keto tautomer. This result coincides with the tautomeric states observed for the BIs in solution (NMR) and in the crystalline state (XRD), and is in line with our earlier calculations on the energetics of BI keto-enol equilibria.

Development of phantom materials with independently adjustable CT- and MR-contrast at 0.35, 1.5 and 3 T

Quality assurance in magnetic resonance (MR)-guided radiotherapy lacks anthropomorphic phantoms that represent tissue-equivalent imaging contrast in both computed tomography (CT) and MR imaging. In this study, we developed phantom materials with individually adjustable CT value as well as [Formula: see text]- and [Formula: see text]-relaxation times in MR imaging at three different magnetic field strengths. Additionally, their experimental stopping power ratio (SPR) for carbon ions was compared with predictions based on single- and dual-energy CT. Ni-DTPA doped agarose gels were used for individual adjustment of [Formula: see text] and [Formula: see text] at [Formula: see text] and 3.0 T. The CT value was varied by adding potassium chloride (KCl). By multiple linear regression, equations for the determination of agarose, Ni-DTPA and KCl concentrations for given [Formula: see text] [Formula: see text] and CT values were derived and employed to produce nine specific soft tissue samples. Experimental [Formula: see text] [Formula: see text] and CT values of these soft tissue samples were compared with predictions and additionally, carbon ion SPR obtained by range measurements were compared with predictions based on single- and dual-energy CT. The measured CT value, [Formula: see text] and [Formula: see text] of the produced soft tissue samples agreed very well with predictions based on the derived equations with mean deviations of less than [Formula: see text] While single-energy CT overestimates the measured SPR of the soft tissue samples, the dual-energy CT-based predictions showed a mean SPR deviation of only [Formula: see text] To conclude, anthropomorphic phantom materials with independently adjustable CT values as well as [Formula: see text] and [Formula: see text] relaxation times at three different magnetic field strengths were developed. The derived equations describe the material specific relaxation times and the CT value in dependence on agarose, Ni-DTPA and KCl concentrations as well as the chemical composition of the materials based on given [Formula: see text] and CT value. Dual-energy CT allows accurate prediction of the carbon ion range in these materials.

IRMPD Spectroscopic and Theoretical Structural Investigations of Zinc and Cadmium Dications Bound to Histidine Dimers

Metallated gas-phase structures consisting of a deprotonated and an intact histidine (His) ligand, yielding M(His-H)(His)⁺, where M = Zn and Cd, were examined with infrared multiple photon dissociation (IRMPD) action spectroscopy utilizing light from a free-electron laser (FEL). In parallel, quantum chemical calculations identified several low-energy isomers for each complex. Experimental action spectra were compared to linear spectra calculated at the B3LYP level of theory using the 6-311+G(d,p) and def2-TZVP basis sets for the zinc and cadmium complexes, respectively. For both Zn and Cd species, the definitive assignment is complicated by conflicting relative energetics, which were calculated at B3LYP, B3LYP-GD3BJ, B3P86, and MP2(full) levels. Spectral comparison for both species indicates that the dominant conformation, [N_α,N_π,CO^-][CO₂^-](N_πH⁺), has the deprotonated His chelating the metal at the amine nitrogen, π nitrogen of the imidazole ring, and the deprotonated carbonyl oxygen and that the intact His ligand adopts a salt-bridge bidentate binding motif, coordinating the metal with both carboxylate oxygens. There is also evidence for a conformation where the deprotonated His coordination is maintained, but the intact His ligand adopts a more canonical structure, coordinating with the metal atom at the amine nitrogen and π nitrogen, [N_α,N_π,CO^-][N_α,N_π]gtgg. For both metallated species, B3LYP, B3P86, and B3LYP-GD3BJ levels of theory appear to describe the relative stability of the dominant zwitterionic species more accurately than the MP2(full) level.

Experimentelle Forschung an der Klinik und Poliklinik für Dermatologie und Venerologie

Seit Antritt von Prof. Dr. med. Steffen Emmert als Ordinarius der Klinik und Poliklinik für Dermatologie und Venerologie im Jahr 2015 konnte das dermatologische Forschungslabor sukzessive aufgebaut und erweitert werden. Im Einklang mit dem onkologischen Schwerpunkt der Universitätsmedizin Rostock sowie dem von der Landesregierung forcierten „Gesundheitsland Mecklenburg-Vorpommern“ wird grundlagenorientierten und translationalen Projekten nachgegangen. Das vorwiegend drittmittelfinanzierte und stetig wachsende Forschungsteam bearbeitet diverse Fragestellungen in den Bereichen der Dermato-Onkologie, Plasmamedizin und seltenen Hauterkrankungen. Inzwischen auf einem soliden Fundament stehend, befindet sich der Forschungsbereich weiterhin in einem dynamischen Entwicklungsprozess. Nicht nur personell, sondern auch thematisch und methodisch wird er derzeit durch die Integration weiterer Arbeitsgruppen unter der Leitung von Ärzten aus der Klinik ergänzt und ausgebaut. Diverse Kollaborationen an der Universitätsmedizin Rostock und im Land zeugen von einem freundlichen, unterstützenden und kollegialen Umfeld, das die Integration am Standort befördert hat.

International multicentre review of perioperative management and outcome for catecholamine-producing tumours

BACKGROUND

Surgery for catecholamine-producing tumours can be complicated by intraoperative and postoperative haemodynamic instability. Several perioperative management strategies have emerged but none has been evaluated in randomized trials. To assess this issue, contemporary perioperative management and outcome data from 21 centres were collected.

METHODS

Twenty-one centres contributed outcome data from patients who had surgery for phaeochromocytoma and paraganglioma between 2000 and 2017. The data included the number of patients with and without α-receptor blockade, surgical and anaesthetic techniques, complications and perioperative mortality.

RESULTS

Across all centres, data were reported on 1860 patients with phaeochromocytoma or paraganglioma, of whom 343 underwent surgery without α-receptor blockade. The majority of operations (78·9 per cent) were performed using minimally invasive techniques, including 16·1 per cent adrenal cortex-sparing procedures. The cardiovascular complication rate was 5·0 per cent overall: 5·9 per cent (90 of 1517) in patients with preoperative α-receptor blockade and 0·9 per cent (3 of 343) among patients without α-receptor blockade. The mortality rate was 0·5 per cent overall (9 of 1860): 0·5 per cent (8 of 517) in pretreated and 0·3 per cent (1 of 343) in non-pretreated patients.

CONCLUSION

There is substantial variability in the perioperative management of catecholamine-producing tumours, yet the overall complication rate is low. Further studies are needed to better define the optimal management approach, and reappraisal of international perioperative guidelines appears desirable.

Short-term flexibility for energy grids provided by wastewater treatment plants with anaerobic sludge digestion

For a sustainable development of the energy sector - in the future - an additional potential of energetic flexibility as well as storage capacities will be required to compensate for fluctuating renewable energy production. The operation of energy systems will change and flexibility in energy generation and consumption will rise to become a valuable asset. Wastewater treatment plants (WWTPs) with anaerobic sludge digestion are capable of providing that needed flexibility, not only with their energy generators but also in terms of their energy consuming aggregates on the plant. Under these circumstances a methodical approach has been developed that can be used to select, evaluate and safely implement typical aggregates on WWTPs for flexible plant operation and the provision of energetic flexibility. Relevant key figures have been developed that reconcile requirements of the purification processes with technical-physical necessities as well as the demands of the energy market. Furthermore, restrictions and control parameters have been established which complement the developed key figures to ensure effluent quality. It was demonstrated that WWTPs are able to adapt their operation mode to external and internal requirements under controlled conditions. The existing flexibility is suitable for a variety of uses, and WWTPs in general are able to participate in today's and in future energy supply products and new business models. The results show that WWTPs have a significant potential to produce renewable energy and to provide energetic flexibility, which is needed to stabilize future renewable-energy-driven energy grids.

Endothelium capture-based liver segment imaging using vascular endothelial growth factor receptor 2 in preclinical ex vivo models

BACKGROUND

Near-infrared (NIR) imaging of liver segments provides substantial information for surgeons performing liver resection. It was hypothesized that ramucirumab, an endothelium-specific antibody approved by the Food and Drug Administration, could be used for liver segment imaging using the endothelium capture principle.

METHODS

The capture efficacy of anti-vascular endothelial growth factor receptor (VEGFR) 2 monoclonal antibodies (mAbs) and segment imaging were studied in a mouse model. Binding of ramucirumab in human and porcine tissues was studied using immunofluorescence staining. Isolated porcine liver perfusion was used to analyse the labelling and NIR imaging of selected liver segments.

RESULTS

VEGFR2 is well expressed on the endothelium of the smallest microvascular blood vessels in mouse, porcine and human liver tissues, as well as in human liver tumours. Perfusion of selected segments in the isolated liver model showed high capture of the anti-VEGFR2 (clone 522302) mAb and ramucirumab in mice and pigs respectively. NIR imaging of selected segments was achieved using isolated porcine liver perfusion with IRDye® 800CW-conjugated ramucirumab.

CONCLUSION

VEGFR2 is well expressed on the smallest microvascular blood vessels and can capture antibodies during single intravascular passages with high efficacy. The ex vivo imaging of a selected segment using endothelial capture of ramucirumab demonstrates the potential of this antibody for intraoperative navigation in liver surgery. Surgical relevance Imaging of liver segments provides substantial information for surgeons when performing liver resection. The antivascular endothelial growth factor receptor (VEGFR) 2 antibody ramucirumab conjugated with near-infrared dye could visualize selected liver segments using an endothelial capture-based approach in an isolated perfusion liver model. The ex vivo imaging of a selected segment using endothelial capture of ramucirumab demonstrates the potential of this anti-VEGFR2 antibody for intraoperative navigation in liver surgery.

[A review of the update of the German S3-guideline on diagnostics and therapy of bipolar disorders 2019]

Since the first publication of the guideline in 2012, which included critically reviewed evidence up to 2010, several hundred articles with new evidence were published and some topics of the clinical consensus needed to be reconsidered. Therefore, it was urgently necessary to revise the guideline to bring them up to date. In this article important revisions and updates are presented and the chances and limitations of the development of the guidelines and their implementation are discussed.

[Current indications for plasma therapy in dermatology]

BACKGROUND

Plasma medicine is gaining increasing interest and provides a multitude of dermatological applications. Cold atmospheric pressure plasma (CAP) can be used in clinical applications without harming the treated tissue or in a tissue destructive manner. It consists of a complex mixture of biologically active agents, which can act synergistically on the treated material or tissue.

OBJECTIVES

A summary of the current research findings regarding dermatological applications of CAP is provided.

METHODS

Literature on CAP applications in dermatology has been screened and summarized.

RESULTS

CAP exerts antimicrobial, tissue-stimulating, blood-flow-stimulating but also pro-apoptotic effects. By exploiting these properties, CAP is successfully applied for disinfection and treatment of chronic ulcerations. Furthermore, positive effects of CAP have been shown for the treatment of tumors, actinic keratosis, scars, ichthyosis, atopic eczema as well as for alleviation of pain and itch.

CONCLUSIONS

While the use of CAP for disinfection and wound treatment has already moved into clinical practice, further applications such as cancer treatment are still exploratory.

The Isotope-Labeled, MS-Cleavable Cross-Linker Disuccinimidyl Dibutyric Urea for Improved Cross-Linking/Mass Spectrometry Studies

Previous studies have shown the benefits of the amine-reactive, CID-MS/MS-cleavable cross-linker disuccinimidyl dibutyric urea (DSBU) for structural proteomics studies via cross-linking/MS (XL-MS). To further facilitate the automation of XL-MS experiments, we synthesized a deuterated (D₁₂) version of the DSBU cross-linker combining the advantages of MS-cleavable linkers and isotope labeling. The rationale of conducting XL-MS with a mixture of unlabeled and stable isotope-labeled DSBU is to obtain characteristic mass differences at the MS level indicating cross-linked species. These cross-linked species can then be selected for fragmentation by collisional activation. At the MS/MS level, the characteristic 26-u doublets arising from cleavage of the central urea group in DSBU confirm the amino acid sequences of cross-linked peptides as well as the exact cross-linking sites. D₁₂-labeled DSBU was tested on three systems with increasing complexity: (i) bovine serum albumin as purified protein, (ii) Escherichia coli ribosome as large, multimeric protein assembly, and (iii) Drosophila embryo extract as complete proteome. We demonstrate the benefits arising from the use of isotope-labeled DSBU for an automated assignment of cross-linked products. Combining isotope labeling and MS cleavability in one cross-linker resulted in higher cross-link identification numbers especially for highly complex protein mixtures.

Olefinic reagents tested for peptide derivatization with switchable properties: Stable upon collision induced dissociation and cleavable by in-source Paternò-Büchi reactions

This contribution is part of our ongoing efforts to develop innovative cross-linking (XL) reagents and protocols for facilitated peptide mixture analysis and efficient assignment of cross-linked peptide products. In this report, we combine in-source Paternò-Büchi (PB) photo-chemistry with a tandem mass spectrometry approach to selectively address the fragmentation of a tailor-made cross-linking reagent. The PB photochemistry, so far exclusively used for the identification of unsaturation sites in lipids and in lipidomics, is now introduced to the field of chemical cross-linking. Based on trans-3-hexenedioic acid, an olefinic homo bifunctional amine reactive XL reagent was designed and synthesized for this proof-of-principle study. Condensation products of the olefinic reagent with a set of exemplary peptides are used to test the feasibility of the concept. Benzophenone is photochemically reacted in the nano-electrospray ion source and forms oxetane PB reaction products. Subsequent CID-MS triggered retro-PB reaction of the respective isobaric oxetane molecular ions and delivers reliably and predictably two sets of characteristic fragment ions of the cross-linker. Based on these signature ion sets, a straightforward identification of covalently interconnected peptides in complex digests is proposed. Furthermore, CID-MSⁿ experiments of the retro-PB reaction products deliver peptide backbone characteristic fragment ions. Additionally, the olefinic XL reagents exhibit a pronounced robustness upon CID-activation, without previous UV-excitation. These experiments document that a complete backbone fragmentation is possible, while the linker-moiety remains intact. This feature renders the new olefinic linkers switchable between a stable, noncleavable cross-linking mode and an in-source PB cleavable mode.

Hydrogen tunneling avoided: enol-formation from a charge-tagged phenyl pyruvic acid derivative evidenced by tandem-MS, IR ion spectroscopy and theory

A charge-tagged phenyl pyruvic acid derivative was investigated by tandem-MS, infrared (IR) ion spectroscopy and theory. The tailor-made precursor ions efficiently lose CO₂ in collision induced dissociation (CID) experiments, offering access to study the secondary decay reactions of the product ions. IR ion spectroscopy provides evidence for the formation of an enol acid precursor ion structure in the gas phase and indicates the presence of enol products formed after CO₂ loss. Extensive DFT computations however, suggest intermediate generation of hydroxycarbene products, which in turn rearrange in a secondary process to the enol ions detected by IR ion spectroscopy. Quantum mechanical tunneling of the hydroxycarbene can be excluded since no evidence for aldehyde product ion formation could be found. This finding is in contrast to the behavior of methylhydroxycarbene, which cleanly penetrates the energy barrier to form exclusively acetaldehyde at cryogenic temperatures in an argon matrix via quantum mechanical hydrogen tunneling. The results presented here are attributed to the highly excited energy levels of the product ions formed by CID in combination with different barrier heights of the competing reaction channels, which allow exclusive access over one energy barrier leading to the formation of the enol tautomer ions observed.

Mosquito bloodmeal preferences in two zoological gardens in Germany

Because they provide a high density and diversity of vertebrate species, small water pools and shaded environments, zoological gardens offer ideal living conditions for numerous mosquito species. Depending on their host preferences and vector competencies, these species may be able to transmit pathogens between native and non-adapted exotic blood host species, thereby causing morbidity and mortality among valuable zoo animals. To determine the extent to which native mosquito species feed on captive and wild animals, as well as on humans, in two German zoological gardens, mosquitoes were collected over two seasons by trapping and aspirating. A total of 405 blood-fed specimens belonging to 16 mosquito taxa were collected. Genetic bloodmeal analysis revealed 56 host species, mainly representing mammals of the zoo animal population, including exotic species previously not known as blood hosts of the mosquito species collected. These results indicate opportunistic feeding patterns with low host-specificity in the analysed mosquitoes, although these could be grouped, according to their bloodmeals, into 'amphibian-', 'non-human mammal-' and 'non-human mammal and human-' feeding species. As the blood-feeding preferences of vector-competent mosquito species are major determinants of vector capacity, information on the blood-feeding behaviour of mosquitoes in zoos is crucial to the success of targeted vector management.

Free radical-initiated peptide sequencing (FRIPS)-based cross-linkers for improved peptide and protein structure analysis

Free radical-initiated peptide sequencing (FRIPS) has recently been introduced as an analytical strategy to create peptide radical ions in a predictable and effective way by collisional activation of specifically modified peptides ions. FRIPS is based on the unimolecular dissociation of open-shell ions and yields fragments that resemble those obtained by electron capture dissociation (ECD) or electron transfer dissociation (ETD). In this review article, we describe the fundamentals of FRIPS and highlight its fruitful combination with chemical cross-linking/mass spectrometry (MS) as a highly promising option to derive complementary structural information of peptides and proteins. FRIPS does not only yield exhaustive sequence information of cross-linked peptides, but also defines the exact cross-linking sites of the connected peptides. The development of more advanced FRIPS cross-linkers that extend the FRIPS-based cross-linking/MS approach to the study of large protein assemblies and protein interaction networks can be eagerly anticipated.

Intermediates of N-Heterocyclic Carbene (NHC) Dimerization Probed in the Gas Phase by Ion Mobility Mass Spectrometry: C-H⋅⋅⋅:C Hydrogen Bonding Versus Covalent Dimer Formation

N-Heterocyclic carbenes (NHCs, :C) can interact with azolium salts (C-H⁺ ) by either forming a hydrogen-bonded aggregate (CHC⁺ ) or a covalent C-C bond (CCH⁺ ). In this study, the intramolecular NHC-azolium salt interactions of aromatic imidazolin-2-ylidenes and saturated imidazolidin-2-ylidenes have been investigated in the gas phase by traveling wave ion mobility mass spectrometry (TW IMS) and DFT calculations. The TW IMS experiments provided evidence for the formation of these important intermediates in the gas phase, and they identified the predominant aggregation mode (hydrogen bond vs. covalent C-C) as a function of the nature of the interacting carbene-azolium pairs.

[Background and current use of adjuvants for regional anesthesia : From research to evidence-based patient treatment]

The discovery of the local anaesthetic effect by blocking sodium ion channels was a milestone in anaesthesia but was soon limited by sometimes life-threatening toxic effects of the local anaesthetics. By developing novel local anaesthetics and also by adding so-called adjuvants, attempts have been made to limit these life-threatening events. This article focuses on the historic background and the current state of the use of these adjuvants for regional anaesthesia. Adding epinephrine, clonidine or dexmedetomidine, but only as a single dose, results in a faster onset, longer duration of action and increased intensity of neuronal blockade of regional anaesthesia. The benefits of adding sodium bicarbonate, on the other hand, are relatively minor and, therefore, clinically negligible. Although increasing evidence in the literature suggests an improvement and prolongation of the analgesic effect after axonal administration of opioids, which can also be given continuously, systemic effects are not fully ruled out due to the increased incidence of central side effects. The partial local anaesthetic effects of opioids cannot always be distinguished from opioid receptor-specific effects. Mechanistic studies postulate a functional coupling of opioid receptors in injured rather than in intact peripheral nerves. Recent studies have identified glucocorticoid and mineralocorticoid receptors predominantly on peripheral nociceptive nerve fibers. This is consistent with numerous clinical reports of a marked prolongation of the local anaesthetic effect. In addition to the known genomic effects of steroids that occur via a change in gene expression of pain-sustaining protein structures, faster non-genomic effects are also discussed, which occur via a change in intracellular signaling pathways. In summary, new insights into mechanisms and novel results from clinical trials will help the anaesthesiologist in the decision to use adjuvants for regional anaesthesia which, however, requires to weigh the individual patient's benefits against the risks.

Calculations ofη-nuclear quasi-bound states in few-body systems

We report on our Stochastic Variational Method (SVM) calculations ofη-nuclear quasi-bound states in s-shell nuclei as well as the very recent calculation of the p-shell nucleus6Li. TheηNpotentials used were constructed fromηNscattering amplitudes obtained within coupled-channel models that incorporateN*(1535) resonance. We found thatη6Li is bound in theηNinteraction models that yield ReaηN≥ 0.67 fm. Additional repulsion caused by the imaginary part ofηNpotentials shifts the onset ofη-nuclear binding toη4He, yielding very likely no quasi-bound state inη3He.

The Ultra-High-Risk for psychosis groups: Evidence to maintain the status quo

Individuals are considered Ultra-High-Risk (UHR) for psychosis if they meet a set of standardised criteria including presumed genetic vulnerability (Trait), or a recent history of Attenuated Psychotic Symptoms (APS) or Brief Limited Intermittent Psychotic Symptoms (BLIPS). Recent calls to revise these criteria have arisen from evidence that Trait, APS and BLIPS groups may transition to psychosis at different rates. Concurrently, it has become clear that the UHR status confers clinical risk beyond transition to psychosis. Specifically, most UHR individuals will not develop psychosis, but will experience high rates of non-psychotic disorders, persistent APS and poor long-term functional outcomes. Rather than focus on transition, the present study investigated whether UHR groups differ in their broader clinical risk profile by examining baseline clinical characteristics and long-term outcomes other than transition to psychosis. Four UHR groups were defined: Trait-only, APS-only, Trait+APS, and any BLIPS. Participants (N=702) were recruited upon entry to early intervention services and followed-up over a period of up to 13years (mean=4.53, SD=3.84). The groups evidenced similar symptom severity (SANS for negative symptoms, BPRS for positive and depression/anxiety symptoms) and psychosocial functioning (SOFAS, GAF, QLS) at baseline and follow-up as well as similar prevalence of non-psychotic disorders at follow-up. Our findings demonstrate that UHR groups evidence a similar clinical risk profile when we expand this beyond transition to psychosis, and consequently support maintaining the existing UHR criteria.

Software-aided quality control of parallel reaction monitoring based quantitation of lipid mediators

We characterized the performance of a micro-flow LC-ESI-MS² approach to analyze lipid mediators (LMs) and polyunsaturated fatty acids (PUFA) that was optimized for SPE free lipid extraction. Tandem mass spectrometry was exclusively performed in parallel reaction monitoring (PRM) mode using TOF and Orbitrap analyzers. This acquisition strategy allowed in addition to quantitation by specific quantifier ions to perform spectrum comparisons using full MS² spectra information of the analyte. Consequently, we developed a dedicated software SpeCS that allows to 1) process raw peak lists, 2) generate customized spectral libraries, 3) test specificity of quantifier ions and 4) perform spectrum comparisons. The dedicated scoring algorithm is based on signal matching and Spearman's rank correlation of intensities of matched signal. The algorithm was evaluated in respect of its specificity to distinguish structural related LMs on both instrument platforms. We show how high resolution mass spectrometry is beneficial to distinguish co-eluted LM isomers and provide a generalized quality control procedure for PRM. The applicability of the approach was evaluated analyzing the lipid mediator response during M. tuberculosis infection in the mouse lung.

Accuracy of preoperative staging for a priori resectable esophageal cancer

This study assessed the accuracy of preoperative staging in patients undergoing oncological esophagectomy for adenocarcinoma and squamous cell carcinoma. All patients undergoing surgery for resectable esophageal cancer in a university hospital from 2005 to 2016 were identified from our institutional database. Patients with neoadjuvant treatment were excluded to avoid bias from down-staging effects. Routinely, all patients had an upper endoscopy with biopsy, a thoracoabdominal CT scan, an 18-FEG PET-CT, and endoscopic ultrasound. Preoperative staging was compared to histopathological staging of surgical specimen that was considered as gold standard. There were 51 patients with a median age of 65 years (IQR: 59.3-73 years) having 21 squamous cell carcinoma and 30 adenocarcinoma, respectively. T- and N-stages were correctly predicted in 26 (51%) and 37 patients (72%), respectively. Overall, 18 patients (35%) were preoperatively diagnosed with a correct T- and N-stage. There was no difference between adenocarcinoma and squamous cell carcinoma. Accuracy of the T-stage was not influenced by the smoking status. The N-stage was not correct in 7/22 smoking patients (32%) and 6/29 nonsmoking patients (21%).The N-stage was underestimated in smoking patients as 6/22 patients (27%) had a histologically confirmed N+ who were preoperatively classified as N0. In conclusion, only 35% of patients had a correct assessment. Separate T- and N-stage prediction was improved with 51% and 72%, respectively. Major efforts are needed for improvement.

Ergothioneine stands out from hercynine in the reaction with singlet oxygen: Resistance to glutathione and TRIS in the generation of specific products indicates high reactivity

The candidate vitamin ergothioneine (ET), an imidazole-2-thione derivative of histidine betaine, is generally considered an antioxidant. However, the precise physiological role of ET is still unresolved. Here, we investigated in vitro the hypothesis that ET serves specifically to eradicate noxious singlet oxygen (¹O₂). Pure ¹O₂ was generated by thermolysis at 37°C of N,N'-di(2,3-dihydroxypropyl)-1,4-naphthalenedipropanamide 1,4-endoperoxide (DHPNO₂). Assays of DHPNO₂ with ET or hercynine (= ET minus sulfur) at pH 7.4 were analyzed by LC-MS in full scan mode to detect products. Based on accurate mass and product ion scan data, several products were identified and then quantitated as a function of time by selected reaction monitoring. All products of hercynine contained, after a [4+2] cycloaddition of ¹O₂, a carbonyl at position 2 of the imidazole ring. By contrast, because of the doubly bonded sulfur, we infer from the products of ET as the initial intermediates a 4,5-dioxetane (after [2+2] cycloaddition) and hydroperoxides at position 4 and 5 (after Schenck ene reactions). The generation of single products from ET, but not from hercynine, was fully resistant to a large excess of tris(hydroxymethyl)aminomethane (TRIS) or glutathione (GSH). This suggests that ¹O₂ markedly favors ET over GSH (at least 50-fold) and TRIS (at least 250-fold) for the initial reaction. Loss of ET was almost abolished in 5mM GSH, but not in 25mM TRIS. Regeneration of ET seems feasible, since some ET products - by contrast to hercynine products - decomposed easily in the MS collision cell to become aromatic again.

Novel Concepts of MS-Cleavable Cross-linkers for Improved Peptide Structure Analysis

The chemical cross-linking/mass spectrometry (MS) approach is gaining increasing importance as an alternative method for studying protein conformation and for deciphering protein interaction networks. This study is part of our ongoing efforts to develop innovative cross-linking principles for a facile and efficient assignment of cross-linked products. We evaluate two homobifunctional, amine-reactive, and MS-cleavable cross-linkers regarding their potential for automated analysis of cross-linked products. We introduce the bromine phenylurea (BrPU) linker that possesses a unique structure yielding a distinctive fragmentation pattern on collisional activation. Moreover, BrPU delivers the characteristic bromine isotope pattern and mass defect for all cross-linker-decorated fragments. We compare the fragmentation behavior of the BrPU linker with that of our previously described MS-cleavable TEMPO-Bz linker (which consists of a 2,2,6,6-tetramethylpiperidine-1-oxy moiety connected to a benzyl group) that was developed to perform free-radical-initiated peptide sequencing. Comparative collisional activation experiments (collision-induced dissociation and higher-energy collision-induced dissociation) with both cross-linkers were conducted in negative electrospray ionization mode with an Orbitrap Fusion mass spectrometer using five model peptides. As hypothesized in a previous study, the presence of a cross-linked N-terminal aspartic acid residue seems to be the prerequisite for the loss of an intact peptide from the cross-linked products. As the BrPU linker combines a characteristic mass shift with an isotope signature, it presents a more favorable combination for automated assignment of cross-linked products compared with the TEMPO-Bz linker. ᅟ.

A Novel MS-Cleavable Azo Cross-Linker for Peptide Structure Analysis by Free Radical Initiated Peptide Sequencing (FRIPS)

The chemical cross-linking/mass spectrometry (MS) approach is a growing research field in structural proteomics that allows gaining insights into protein conformations. It relies on creating distance constraints between cross-linked amino acid side chains that can further be used to derive protein structures. Currently, the most urgent task for designing novel cross-linking principles is an unambiguous and automated assignment of the created cross-linked products. Here, we introduce the homobifunctional, amine-reactive, and water soluble cross-linker azobisimidoester (ABI) as a prototype of a novel class of cross-linkers. The ABI-linker possesses an innovative modular scaffold combining the benefits of collisional activation lability with open shell chemistry. This MS-cleavable cross-linker can be efficiently operated via free radical initiated peptide sequencing (FRIPS) in positive ionization mode. Our proof-of-principle study challenges the gas phase behavior of the ABI-linker for the three amino acids, lysine, leucine, and isoleucine, as well as the model peptide thymopentin. The isomeric amino acids leucine and isoleucine could be discriminated by their characteristic side chain fragments. Collisional activation experiments were conducted via positive electrospray ionization (ESI) on two Orbitrap mass spectrometers. The ABI-mediated formation of odd electron product ions in MS/MS and MS³ experiments was evaluated and compared with a previously described azo-based cross-linker. All cross-linked products were amenable to automated analysis by the MeroX software, underlining the future potential of the ABI-linker for structural proteomics studies. Graphical Abstract ᅟ.

Energetic flexibility on wastewater treatment plants

In the future, an additional potential of control reserve as well as storage capacities will be required to compensate fluctuating renewable energy availability. The operation of energy systems will change and flexibility in energy generation and consumption will rise to a valuable asset. Wastewater treatment plants (WWTPs) are capable of providing the flexibility needed, not only with their energy generators but also in terms of their energy consuming aggregates on the plant. To meet challenges of the future in regard to energy purchase and to participate in and contribute to such a volatile energy market, WWTPs have to reveal their energetic potential as a flexible service provider. Based on the evaluated literature and a detailed analysis of aggregates on a pilot WWTP an aggregate management has been developed to shift loads and provide a procedure to identify usable aggregates, characteristic values and control parameters to ensure effluent quality. The results show that WWTPs have a significant potential to provide energetic flexibility. Even for vulnerable components such as aeration systems, load-shifting is possible with appropriate control parameters and reasonable time slots without endangering system functionality.

Randomised clinical trial: yoga vs written self-care advice for ulcerative colitis

BACKGROUND

Perceived stress seems to be a risk factor for exacerbation of ulcerative colitis. Yoga has been shown to reduce perceived stress.

AIMS

To assess the efficacy and safety of yoga for improving quality of life in patients with ulcerative colitis.

METHODS

A total of 77 patients (75% women; 45.5 ± 11.9 years) with ulcerative colitis in clinical remission but impaired quality of life were randomly assigned to yoga (12 supervised weekly sessions of 90 min; n = 39) or written self-care advice (n = 38). Primary outcome was disease-specific quality of life (Inflammatory Bowel Disease Questionnaire). Secondary outcomes included disease activity (Rachmilewitz clinical activity index) and safety. Outcomes were assessed at weeks 12 and 24 by blinded outcome assessors.

RESULTS

The yoga group had significantly higher disease-specific quality of life compared to the self-care group after 12 weeks (Δ = 14.6; 95% confidence interval=2.6-26.7; P = 0.018) and after 24 weeks (Δ = 16.4; 95% confidence interval=2.5-30.3; P = 0.022). Twenty-one and 12 patients in the yoga group and in the self-care group, respectively, reached a clinical relevant increase in quality of life at week 12 (P = 0.048); and 27 and 17 patients at week 24 (P = 0.030). Disease activity was lower in the yoga group compared to the self-care group after 24 weeks (Δ = -1.2; 95% confidence interval=-0.1-[-2.3]; P = 0.029). Three and one patient in the yoga group and in the self-care group, respectively, experienced serious adverse events (P = 0.317); and seven and eight patients experienced nonserious adverse events (P = 0.731).

CONCLUSIONS

Yoga can be considered as a safe and effective ancillary intervention for patients with ulcerative colitis and impaired quality of life.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02043600.

Hydrogen Tunneling above Room Temperature Evidenced by Infrared Ion Spectroscopy

While hydrogen tunneling at elevated temperatures has, for instance, often been postulated in biochemical processes, spectroscopic proof is thus far limited to cryogenic conditions, under which thermal reactivity is negligible. We report spectroscopic evidence for H-tunneling in the gas phase at temperatures around 320-350 K observed in the isomerization reaction of a hydroxycarbene into an aldehyde. The charge-tagged carbene was generated in situ in a tandem mass spectrometer by decarboxylation of oxo[4-(trimethylammonio)phenyl]acetic acid upon collision induced dissociation. All ion structures involved are characterized by infrared ion spectroscopy and quantum chemical calculations. The charge-tagged phenylhydroxycarbene undergoes a 1,2-H-shift to the corresponding aldehyde with an half-life of about 10 s, evidenced by isomer-selective two-color (IR-IR) spectroscopy. In contrast, the deuterated (OD) carbene analogue showed much reduced 1,2-D-shift reactivity with an estimated half-life of at least 200 s under the experimental conditions, and provides clear evidence for hydrogen atom tunneling in the H-isotopologue. This is the first spectroscopic confirmation of hydrogen atom tunneling governing 1,2-H-shift reactions at noncryogenic temperatures, which is of broad significance for a range of (bio)chemical processes, including enzymatic transformations and organocatalysis.