Time-Resolved Ultraviolet Photodissociation Mass Spectrometry Probes the Mutation-Induced Alterations in Protein Stability and Unfolding Dynamics.

How mutations impact protein stability and structure dynamics is crucial for understanding the pathological process and rational drug design. Herein, we establish a time-resolved native mass spectrometry (TR-nMS) platform via a rapid-mixing capillary apparatus for monitoring the acid-initiated protein unfolding process. The molecular details in protein structure unfolding are further profiled by a 193 nm ultraviolet photodissociation (UVPD) analysis of the structure-informative photofragments. Compared with the wild-type dihydrofolate reductase (WT-DHFR), the M42T/H114R mutant (MT-DHFR) exhibits a significant stability decrease in TR-nMS characterization. UVPD comparisons of the unfolding intermediates and original DHFR forms indicate the special stabilization effect of cofactor NADPH on DHFR structure, and the M42T/H114R mutations lead to a significant decrease in NADPH-DHFR interactions, thus promoting the structure unfolding. Our study paves the way for probing the mutation-induced subtle changes in the stability and structure dynamics of drug targets.

Factors predicting indistinct plane of surgical capsule in patients underwent HoLEP procedures.

PURPOSE: To evaluate factors that effectively predict indistinct plane (IP) in patients who underwent holmium laser enucleation of the prostate (HoLEP). METHODS: Data of 208 consecutive patients from our HoLEP database were reviewed and analyzed. IP was defined in 107 cases, as the plane could be identified only depending on endoscopic beak dissection rather than laser dissection in the initial stage of HoLEP, whereas the control group consisted of 101 cases. Variables including age, body mass index, prostatic volume (PV), intravesical prostatic protrusion, prostate-specific antigen, prostate-specific antigen density, bladder stones, urinary tract infection, microscopic hematuria, prior biopsy (PB), diabetes, hypertension, history of acute urinary retention, 5-alpha reductase inhibitor treatment, catheter dependency, residual urine, region, smoking, and alcohol consumption were compared between the two groups. The risk factors for predicting the presence of IP were determined using a multivariable binary logistic regression model using a forward selection approach with a focus on improvement in the area under the receiver operating characteristic curve (AUC). RESULTS: The incidence of IP was 51.4% (107/208). PV (OR = 0.977, p < 0.001) and PB (OR = 0.297, p = 0.028) were identified as the independent predictors of capsule plane status. PV with a cutoff of 54 ml had the best predictive effectiveness for IP based on AUC (0.727; 95% CI 0.659-0.795). The specificity and sensitivity of this cutoff were 82.2% and 53.3%, respectively. CONCLUSION: PV is the most reliable factor to predict IP during HoLEP procedures. There is a high possibility of IP in patients with a PV less than 54 ml.

Vibration to Vibration: Product Energy Distribution of F + HD Crossed Molecular Beam Experiments.

We investigated the F + HD(v = 1, j = 0) → HF + D reaction using the crossed molecular beam technique combined with the D atom Rydberg tagging time-of-flight spectroscopy. By detecting the products at various scattering angles for different collision energies in the range of 0.8-1.2 kcal/mol, we observed the forward-scattering products of HF(v' = 4) and determined the threshold energy for the opening of this reaction channel. Similar experiments were conducted for the F + HD(v = 0, j = 0) → HF + D reaction within the range of 1.1-1.6 kcal/mol, where forward-scattering products of HF(v' = 3) were observed, and the threshold energy for this reaction channel was determined as well. Furthermore, we measured the differential cross-sections for the F + HD → HF + D reaction in both the vibrational ground state and the excited state of HD and analyzed the vibrational quantum-state distribution of the HF products. It was found that the population of vibrational quantum states of the HF products increases synchronously with the excitation of the reactant HD vibrationally.

Unraveling the Photodissociation Branching and Pathways of Methane at 118 nm by Imaging the CH3, CH2, and CH Fragments.

Under irradiation of a vacuum ultraviolet (VUV) photon, methane dissociates and yields multiple fragments. This photochemical behavior is not only of fundamental importance but also with wide-ranging implications in several branches of science. Despite that and numerous previous investigations, the product channel branching is still under debate, and the underlying dissociation mechanisms remain elusive. In this study, the photofragment imaging technique was exploited for the first time to map out the momentum and anisotropy parameter distributions of the CH3, CH2, and CH fragments at the 118 nm photolysis wavelength (10.48 eV photon energy). In conjunction with previously reported results of the H atom fragment at 121.6 nm (10.2 eV), a complete set of product channel branching in both two-body and three-body fragmentations is accurately determined. We concluded that extensive nonadiabatic transitions partake in the processes with two-body fragmentations accounting for more than 90% of overall photodissociation, for which the channel branching values for CH2 + H2 and CH3 + H are about 0.66 and 0.25, respectively. Careful kinematic analysis enables us to untangle the intertwined triple fragmentations into the CH2(X̃ 3B1 and ã 1A1) + H + H and CH(X2Π) + H + H2 channels and to evidence their underlying sequential (or stepwise) mechanisms. With the aid of electronic correlation and prior theoretical calculations of the potential energy surfaces, the most probable or dominant dissociation pathways are elucidated. Comparisons with fragmentary reports in the literature on various photochemical aspects are also documented, and discrepancies are clarified. This comprehensive study benchmarks the VUV photochemistry of methane and advances our understanding of this important process.

Reaction Kinetics of CH2OO and syn-CH3CHOO Criegee Intermediates with Acetaldehyde.

Criegee intermediates exert a crucial influence on atmospheric chemistry, functioning as powerful oxidants that facilitate the degradation of pollutants, and understanding their reaction kinetics is essential for accurate atmospheric modeling. In this study, the kinetics of CH2OO and syn-CH3CHOO reactions with acetaldehyde (CH3CHO) were investigated using a flash photolysis reaction tube coupled with the OH laser-induced fluorescence (LIF) method. The experimental results indicate that the reaction of syn-CH3CHOO with CH3CHO is independent of pressure in the range of 5-50 Torr when using Ar as the bath gas. However, the rate coefficient for the reaction between CH2OO and CH3CHO at 5.5 Torr was found to be lower compared to the near-constant values observed between 10 and 100 Torr. Furthermore, the reaction of syn-CH3CHOO with CH3CHO demonstrated positive temperature dependence from 283 to 330 K, with a rate coefficient of (2.11 ± 0.45) × 10-13 cm3 molecule-1 s-1 at 298 K. The activation energy and pre-exponential factor derived from the Arrhenius plot for this reaction were determined to be 2.32 ± 0.49 kcal mol-1 and (1.66 ± 0.61) × 10-11 cm3 molecule-1 s-1, respectively. In comparison, the reaction of CH2OO with CH3CHO exhibited negative temperature dependence, with a rate coefficient of (2.16 ± 0.39) × 10-12 cm3 molecule-1 s-1 at 100 Torr and 298 K and an activation energy and a pre-exponential factor of -1.73 ± 0.31 kcal mol-1 and (1.15 ± 0.21) × 10-13 cm3 molecule-1 s-1, respectively, over the temperature range of 280-333 K.

Strong Angular Oscillation of Rotationally Resolved Differential Cross Section in the H + HD → H2 + D Reaction at the Collision Energy of 2.07 eV: Evidence of Geometric Phase Effects.

Geometric phase (GP) effects in chemical reactions are subtle quantum phenomena that are challenging to identify. In this work, we report a joint experimental and theoretical study of the H + HD → H2 + D reaction at a collision energy of 2.07 eV, which is far below the energy of the conical intersection of 2.53 eV. The rotationally state-resolved differential cross sections were measured by a crossed-beam experiment with the scheme of D-atom Rydberg tagging time-of-flight detection. Experimental angular distributions of three rotational states of H2 products exhibit notable variation near the backward scattering direction. Time-dependent quantum mechanics calculations (TDQMs) were carried out at the same collision energy, with and without the inclusion of GP. The experimental angular distributions are in good agreement with TDQM results with the inclusion of GP but do not agree with TDQM results without the inclusion of GP. This work demonstrates the existence of GP effects at energy far below the conical intersection.

Polymeric Metal Halides with Bright Luminescence and Versatile Processability.

Most of current metal halide materials, including all inorganic and organic-inorganic hybrids, are crystalline materials with poor workability and plasticity that limit their application scope. Here, we develop a novel class of materials termed polymeric metal halides (PMHs) through introducing polycations into antimony-based metal halide materials as A-site cations. A series of PMHs with orange-yellow broadband emission and large Stokes shift originating from inorganic self-trapped excitons are successfully prepared, which meanwhile exhibit the excellent processability and formability of polymers. The versatility of these PMHs is manifested as the broad choices of polycations, the ready extension to manganese- and copper-based halides, and the tolerance to molar ratios between polycations and metal halides in the formation of PMHs. The merger of polymer chemistry and inorganic chemistry thus provides a novel generic platform for the development of metal halide functional materials.

Ultraviolet Photodissociation Reveals the Molecular Mechanism of Crown Ether Microsolvation Effect on the Gas-Phase Native-like Protein Structure.

Maintaining the protein high-order structures and interactions during the transition from aqueous solution to gas phase is essential to the structural analysis of native mass spectrometry (nMS). Herein, we systematically interrogate the effects of charge state and crown ether (CE) complexation on the gas-phase native-like protein structure by integrating nMS with 193 nm ultraviolet photodissociation (UVPD). The alterations of photofragmentation yields of protein residues and the charge site distribution of fragment ions reveal the specific sites and sequence regions where charge and CE take effect. Our results exhibit the CE complexation on protonated residues can largely alleviate the structure disruption induced by the intramolecular solvation of charged side chains. The influences of CE complexation and positive charge on gas-phase protein structure exhibit generally opposite trends because the CE microsolvation avoids the hydrogen-bonding formation between the charged side chains with backbone carbonyls. Thus, CE complexation leads to a more stable and native-like protein structure in the gas phase.

Molecular Structure Characterization of Micro/Nanoplastics by 193 nm Ultraviolet Photodissociation Mass Spectrometry.

The degradation of macroplastics results in micro/nanoplastics (MNPs) in the natural environment, inducing high health risks worldwide. It remains challenging to characterize the accurate molecular structures of MNPs. Herein, we integrate 193 nm ultraviolet photodissociation (UVPD) with mass spectrometry to interrogate the molecular structures of poly(ethylene glycol) terephthalate and polyamide (PA) MNPs. The backbones of the MNP polymer can be efficiently dissociated by UVPD, producing rich types of fragment ions. Compared to high-energy collision dissociation (HCD), the structural informative fragment ions and corresponding sequence coverages obtained by UVPD were all improved 2.3 times on average, resulting in almost complete sequence coverage and precise structural interrogation of MNPs. We successfully determine the backbone connectivity differences of MNP analogues PA6, PA66, and PA610 by improving the average sequence coverage from 26.8% by HCD to 89.4% by UVPD. Our results highlight the potential of UVPD in characterizing and discriminating backbone connectivity and chain end structures of different types of MNPs.

Chloride-Mediated Peroxide-Free Photochemical Oxidation of Proteins (PPOP) in Mass Spectrometry-Based Structural Analysis.

Ultraviolet (UV) laser photolysis of hydrogen peroxide (H2O2) for the in situ generation of hydroxyl radicals (•OH) is a widely utilized strategy in the oxidation footprinting of native proteins and mass spectrometry (MS)-based structural analysis. However, it remains challenging to realize peroxide-free photochemical oxidation footprinting. Herein, we describe the footprinting of native proteins by chloride-mediated peroxide-free photochemical oxidation of proteins (PPOP). The protein samples are prepared within biocompatible phosphate-buffered saline (PBS) containing 10 mM Gln as radical scavengers and oxidized in a capillary flow reactor directly under a single-pulse (10 ns) irradiation of a 193 nm ArF UV laser. The main oxidized protein residues are CMYWFHLI. We demonstrate that the PPOP-MS strategy is highly sensitive to the protein high-order structures and can be applied to monitor the protein-drug interfaces, which provides a promising footprinting alternative for protein structure-function explorations.

'Seven-step two-lobe' HoLEP: a modification to gain efficiency of the enucleation applying relatively low-power holmium laser devices.

PURPOSE: In order to increase the efficiency of the low-power holmium laser enucleation of the prostate (LP-HoLEP), and introduce it as a standard surgery for BPH, we described a modified 'seven-step two-lobe' HoLEP (ST HoLEP) technique applying 60-W device in a stepwise manner. METHODS: From July 2016 to August 2019, 120 patients who received LP-HoLEP at our hospital because of urinary tract symptoms caused by BPH were included in the study. The patients were assigned into two groups, 60 consecutive patients received modified ST HoLEP compared with another preexisting 60 consecutive patients who received the conventional three-lobe HoLEP (T HoLEP) before the technical modification. The clinical parameters, including patient characteristics, perioperative data, as well as voiding outcomes, and complications were evaluated after at least 3-month follow-up. RESULTS: The median enucleation efficiency of the ST HoLEP was 0.72 gm/min, which was significantly higher than 0.62 gm/min of the T HoLEP. Despite the preoperative IPSS was slightly higher in T HoLEP group, the other preoperative and perioperative data showed no statistical difference between the two groups. After ST HoLEP procedure, the urinary incontinence rate was continually improved at 1-week, 1-month, and 3-month follow-up which were 13.3%, 6.7%, and 1.7%, respectively. There was no significant difference in postoperative voiding outcomes and urinary continence results in 3-month follow-up. CONCLUSION: The ST HoLEP technique was proved to increase the efficiency which was benefit from minimizing the surgical incision, facilitating the single surgical plane identification and maintenance during the whole enucleation procedure.

Temperature- and pressure-dependent rate coefficient measurement for the reaction of CH2OO with CH3CH2CHO.

Propionaldehyde is one of the most abundant aldehydes, which are an important class of volatile organic compounds. In this work, the rate coefficient of the reaction of the simplest Criegee intermediate CH2OO with propionaldehyde (CH3CH2CHO) was measured for the first time in a flash photolysis reaction tube by using the OH laser-induced fluorescence (LIF) method at temperature and pressure in the range of 283 to 318 K and 5 to 200 Torr. This reaction is observed to be pressure- and temperature-dependent. The measured rate coefficient at 50 Torr is in the vicinity of the high-pressure limit value of (3.23 ± 0.49) × 10-12 cm3 s-1 at 298 K, which is in agreement with a previously reported theoretical result of 2.44 × 10-12 cm3 s-1. The Arrhenius plot of the temperature-dependent rate coefficients yields an activation energy of (-1.99 ± 0.23) kcal mol-1.

Kinetic Studies for the Reaction of syn-CH3CHOO with CF3CH═CH2.

Hydrofluoroolefins (HFOs, CxF2x+1CH═CH2) have great potential to replace hydrofluorocarbons (HFCs) as refrigerants. Here the kinetics for the reaction of syn-CH3CHOO with CF3CH═CH2 (HFO-1243zf), the simplest of HFOs, have been studied in a flash photolysis flow reactor at a total pressure of 50 Torr, by using the OH laser-induced fluorescence (LIF) method. The bimolecular reaction rate coefficients were measured at temperatures ranging from 283 to 318 K. A weak positive temperature dependence was observed, with an activation energy of 1.41 ± 0.12 kcal mol-1. At 298 K, the measured rate coefficient was (2.42 ± 0.51) × 10-14 cm3 s-1, in the vicinity of the previously reported upper limit value for the reaction of CH2OO with CF3CH═CH2.

Experimental and Theoretical Study of the Vibrationally Excited Reaction Cl + D2 (v = 1, j = 0) → DCl + D.

Vibrationally excited reaction of Cl + D2 (v = 1, j = 0) → DCl + D was investigated by a high-resolution crossed beam experiment, with D2 molecules in the vibrationally excited state prepared by the scheme of stimulated Raman pumping. Differential cross sections (DCSs) were obtained at three collision energies of 4.03, 4.93, and 5.68 kcal/mol. Backward scattering is dominant for both DCl (v' = 0) and DCl (v' = 1) products, and no forward scattering signal was observed at these three collision energies. Collision-energy-dependent DCS in the backward scattering direction was measured at collision energies between 3.62 and 5.97 kcal/mol. Comparing with the DCSs from the vibrational ground state, it is found that the vibrational excitation of D2 molecules significantly enhances the reactivity because of the later barrier nature of the reaction. No obvious oscillatory structure was found in the collision-energy-dependent DCS in the backward scattering direction, suggesting that the title reaction proceeds via a direct abstraction mechanism.

Impact of Preoperative Magnetic Resonance Imaging Anatomic Features on Urinary Continence Recovery after Laparoscopic Radical Prostatectomy.

PURPOSE: To evaluate the impact of preoperative magnetic resonance imaging anatomic features on urinary continence recovery after laparoscopic radical prostatectomy (LRP). METHODS: We retrospectively analyzed 150 consecutive prostate cancer patients who underwent LRP between July 2015 and June 2018 in our institution. Patients reporting freedom from using safety pad (0 pads/day) were defined as urinary continent. We evaluated the association of urinary continence recovery after LRP and the perioperative variables, including age, prostatic volume (PV), intravesical prostatic protrusion length (IPPL), membranous urethral length (MUL), and neurovascular bundle (NVB) sparing status. Kaplan-Meier and log-rank tests were used to compare urinary continence rates between groups. Univariate and multivariate Cox proportional hazards regression analyses were used to identify independent predictors for urinary continence recovery. RESULTS: 60.6% (91/150), 83.3% (125/150), and 96.0% (144/150) of the patients experienced urinary continence recovery at 3, 6, and 12 months, respectively. There was significant difference in PV, IPPL, MUL, and NVB sparing between groups stratified by urinary continence status at 3, 6, and 12 months. Kaplan-Meier curves of urinary continence rates showed significant differences between groups stratified by PV (<50 mL vs. ≥50 mL, p < 0.001), IPPL (<5 mm vs. ≥5 mm, p < 0.001), MUL (≥15 mm vs. <15 mm, p < 0.001), and NVB sparing status (yes vs. no, p = 0.003), respectively. On univariate analysis, PV, IPPL, MUL, and NVB sparing were significantly associated with urinary continence recovery (all, p < 0.05). On multivariate analysis, only IPPL (HR = 0.94, p = 0.003) and MUL (HR = 1.10, p < 0.001) were independent predictors for urinary continence recovery. CONCLUSION: Patients with larger IPPL and shorter MUL have higher chances of delayed recovery of urinary continence after LRP. IPPL and MUL were reliable morphometric parameters for predicting urinary continence.

Dynamical resonances in chemical reactions.

The transition state is a key concept in the field of chemistry and is important in the study of chemical kinetics and reaction dynamics. Chemical reactions in the gas phase are essentially molecular scattering processes, which are quantum mechanical in nature. Thus probing and understanding detailed quantum structure in the transition state region of chemical reactions, such as reactive resonances, is a central topic in this field. In this article, we focus on recent progress in the study of resonances in elementary bimolecular reactions using state-of-the-art transition state spectroscopy methods: high-resolution photoelectron spectroscopy and quantum state specific backward scattering spectroscopy. The experimental results are compared with high-level quantum dynamics calculations based on highly accurate potential energy surfaces. The dynamics of reactive resonances are also interpreted based on scattering wavefunctions obtained by time-dependent wavepacket calculations. Here, we review many systems that illustrate how reactive resonances can strongly influence the dynamics of elementary chemical reactions.

Kinetics of the reaction of the simplest Criegee intermediate with ammonia: a combination of experiment and theory.

The kinetics of the reaction of the simplest Criegee intermediate (CH2OO) with ammonia has been measured under pseudo-first-order conditions with two different experimental methods. We investigated the rate coefficients at 283, 298, 308, and 318 K at a pressure of 50 Torr using an OH laser-induced fluorescence (LIF) method. Weak temperature dependence of the rate coefficient was observed, which is consistent with the theoretical activation energy of -0.53 kcal mol-1 predicted by quantum chemistry calculation at the QCISD(T)/CBS//B3LYP/6-311+G(2d,2p) level. At 298 K, the rate coefficient at 50 Torr from the OH LIF experiment was (5.64 ± 0.56) × 10-14 cm3 molecule-1 s-1 while at 100 Torr we obtained a slightly larger value of (8.1 ± 1.0) × 10-14 cm3 molecule-1 s-1 using the UV transient absorption method. These experimental values are within the theoretical error bars of the present as well as previous theoretical results. Our experimental results confirmed the previous conclusion that ammonia is negligible in the consumption of CH2OO in the atmosphere. We also note that CH2OO may compete with OH in the oxidation of ammonia under certain circumstances, such as at night-time, high altitude and winter time.

Effect of Reagent Vibrational Excitation on the Dynamics of F + H2(v = 1, j = 0) → HF(v', j') + H Reaction.

The reaction of fluorine atom with vibrationally excited H2 at v = 1 has been studied using a high resolution crossed molecular beam apparatus at collision energies of 0.52 and 0.90 kcal/mol. Product HF rotational state-resolved differential cross sections (DCSs) were measured at v' = 2, 3, 4 levels. The product angular distributions are predominantly backward scattered except for a small forward signal of HF(v' = 4) at 0.90 kcal/mol. At the collision energy of 0.52 kcal/mol, the forward scattering peak of the HF(v' = 2) product, which arises in F + H2(v = 0) reaction from the Feshbach resonances, disappears in F + H2(v = 1) reaction. Oscillatory structures do not appear in the backward direction of the scattering as the collision energy increases from 0.4 to 2.0 kcal/mol, indicating there are no explicit reaction resonances in the F + H2(v = 1, j = 0) → HF + H reaction in the studied energy range. Quantum dynamics calculations on a highly accurate potential energy surface are in good agreement with the experimental results and reveal that the reaction occurs via likely a direct abstraction mechanism, not via long-lived reactive resonances.

[Management of calyceal diverticular calculi with stenotic infundibulum by flexible ureteroscopic holmium laser infundibulectomy and lithotripsy].

OBJECTIVE: To evaluate the efficacy and safety of flexible ureteroscopic holmium laser lithotripsy in treating calyceal diverticular calculi with stenotic infundibulum and to present our initial experience. METHODS: From Nov. 2012 to Nov. 2014, 10 patients with stone-bearing calyceal diverticulum and stenotic infundibulum underwent flexible ureteroscopic holmium laser lithotripsy in our hospital, including 3 female patients and 7 male patients with an average age of 36.9 years (range: 20 to 62 years). There were 6 patients with right side while 4 patients with left side calyceal diverticular calculi. The average cumulative stone size was (1.33±0.43) cm. Five patients underwent extracorporeal shock wave lithotripsy (ESWL) before hospital admission but no stone was discharged. All the patients received intravenous urography (IVU) and CT-urography (CTU) preoperatively and underwent double-J stents placement 2 weeks before operations. A digital-fiber flexible ureteroscopy and 200 µm holmium laser fiber were used for treatment. Surgeries began with routine flexible ureteroscopy and methylene blue injection was used to identify the small ostium of infundibulum. Then infundibulectomy followed by lithotripsy was performed. All the patients receive double-J stents placement and traditional Chinese medicine for 1 to 3 months after operations. The stone clearance was estimated by kidney ureter bladder (KUB) within 3 months' follow up. RESULTS: The locations of calyceal diverticulum were upper pole in 7 patients, and interpolar regions in 4 patients. The average operation time was (123.7±59.6) min, and the average estimated blood loss was (29.3±32.1) mL. Successful flexible ureteroscopic holmium laser infundibulectomies were performed in all the 10 patients. Success rate was 100%. The stone clearance rates for 1 and 3 months after surgery were 50.0% and 80.0%, respectively, which were observed by KUB follow-up. Two patients had serious post-operative fever (>38.0 °C) in coexistence with chills. The mobidity of urosepsis was 20.0%. No major complications were identified. CONCLUSION: In selected patients, calyceal diverticular calculi with stenotic infundibulum can be treated safely and efficiently with flexible ureteroscopic homium laser lithotripsy. CTU and IVU should be completed preoperatively for calyceal diverticulum location and technique difficulty prediction. Retrograde methylene blue injection can be used to identify the ostium during surgery. And prolonged post-operation stone clearance was observed.