Cryogenic Experiments Research Articles

Influence of bimodal non-basal texture on microstructure characteristics, texture evolution and deformation mechanisms of AZ31 magnesium alloy sheet rolled at liquid-nitrogen temperature

Cryogenic rolling experiments have been conducted on the AZ31 magnesium (Mg) alloy sheet with bimodal non-basal texture, which is fabricated via the newly developed equal channel angular rolling and continuous bending process with subsequent annealing (ECAR-CB-A) process. Results demonstrate that this sheet shows no edge cracks until the accumulated thickness reduction reaches about 18.5%, which is about 105.6% larger than that of the sheet with traditional basal texture. Characterization experiments including optical microstructure (OM), X-ray diffractometer (XRD), and electron backscatter diffraction (EBSD) measurements are then performed to explore the microstructure characteristics, texture evolution and deformation mechanisms during cryogenic rolling. Experimental observations confirm the occurrence of abundant {10–12} extension twins (ETs), twin-twin interactions among {10–12} ET variants and {10–12}-{10–12} double twins (DTs). The twinning behaviors as for {10–12} ETs are responsible for the concentration of c-axes of grains towards normal direction (ND) and the formation of transverse direction (TD)-component texture at the beginning of cryogenic rolling. The twinning behaviors with respect to {10–12}-{10–12} DTs are responsible for the disappearance of TD-component texture at the later stage of cryogenic rolling. The involved deformation mechanisms can be summarized as follows: Firstly {10–12} ETs dominate the plastic deformation. Subsequently, dislocation slip, especially basal <a> slip, starts to sustain more plastic strain, while {10–12} ETs occur more frequently and enlarge continuously, resulting in the formation of twin-twin interaction among {10–12} ET variants. With the increasing rolling passes, {10–12}-{10–12} DTs incorporate in the plastic deformation and dislocation slip serves as the major one to sustain plastic strain. The activities of basal <a> slip, {10–12} ETs and {10–12}-{10–12} DTs benefit in accommodating the plastic strain in sheet thickness, which contributes to the improved rolling formability in AZ31 Mg alloy sheet with bimodal non-basal texture during cryogenic rolling.

Water film thickness of tight reservoir in Fuyu oil layer of Cretaceous Quantou Formation in Songliao Basin and its influence on the lower limit of seepage

The water film thickness in tight sandstone reservoir is critical to determine the lower limit of both flow pore-throat radius and the physical property of the reservoir. In order to study the effect of water film thickness on fluid flow capacity, firstly, through molecular dynamics simulations, the adsorption behavior of different minerals on water molecules was simulated, and the adsorption characteristics of different minerals on water molecules were clarified. Secondly, a new method for calculating the water film thickness of bound water was established by comprehensively using three experimental methods: high-pressure mercury injection experiment (HPMI), cryogenic nitrogen adsorption experiment, and centrifugal-nuclear magnetic resonance (NMR). The lower limit of the flow pore-throat radius and the physical property of the tight reservoir were determined more accurately by improving the previous calculation methods. The results demonstrated that the adsorption of minerals to water molecules mainly formed a binding force through microscopic forces such as electrostatic force and Van Der Waals Force, in which Van Der Waals Force repels water molecules while electrostatic force absorbs water molecules. Different minerals have different adsorption capacities for water molecules. According to the established formula, the bound water film thickness of different samples is different. Then, the water film thickness of the Fuyu oil layer in the Songliao Basin can be calculated to be approximately 19.651 nm. By improving the formula used by the predecessors to determine the lower limit of physical property, it could be accurately determined that the lower limit of flow pore-throat radius was 26.751 nm, and the lower limit of permeability and porosity was 0.047mD and 9.87%, respectively. This method has both a strong theoretical basis and experimental data support. Thus, it can be generalized to a certain extent.

Custom metallic electron microscopy grids reduce sample heating in super-resolved cryogenic correlative light and electron microscopy experiments

Super-resolved cryogenic correlative light and electron microscopy (srCryoCLEM) is an exciting new method that can determine the positions of specifically labelled biomolecules of interest in the context of cryogenic electron tomography (CET) reconstructions. These srCryoCLEM experiments are conducted by sequentially performing cryogenic superresolution fluorescence followed by CET. Biological samples for srCryoCLEM are rapidly frozen to preserve the sample in its native hydrated state. Further, this rapid freezing produces amorphous (vitreous) ice as opposed to crystalline ice that would obscure the transmitted electron beam.

Ice nucleation imaged with X-ray spectro-microscopy.

Ice nucleation is one of the most uncertain microphysical processes, as it occurs in various ways and on many types of particles. To overcome this challenge, we present a heterogeneous ice nucleation study on deposition ice nucleation and immersion freezing in a novel cryogenic X-ray experiment with the capability to spectroscopically probe individual ice nucleating and non-ice nucleating particles. Mineral dust type particles composed of either ferrihydrite or feldspar were used and mixed with organic matter of either citric acid or xanthan gum. We observed in situ ice nucleation using scanning transmission X-ray microscopy (STXM) and identified unique organic carbon functionalities and iron oxidation state using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy in the new in situ environmental ice cell, termed the ice nucleation X-ray cell (INXCell). Deposition ice nucleation of ferrihydrite occurred at a relative humidity with respect to ice, RHi, between ∼120–138% and temperatures, T ∼ 232 K. However, we also observed water uptake on ferrihydrite at the same T when deposition ice nucleation did not occur. Although, immersion freezing of ferrihydrite both in pure water droplets and in aqueous citric acid occurred at or slightly below conditions for homogeneous freezing, i.e. the effect of ferrihydrite particles acting as a heterogeneous ice nucleus for immersion freezing was small. Microcline K-rich feldspar mixed with xanthan gum was also used in INXCell experiments. Deposition ice nucleation occurred at conditions when xanthan gum was expected to be highly viscous (glassy). At less viscous conditions, immersion freezing was observed. We extended a model for heterogeneous and homogeneous ice nucleation, named the stochastic freezing model (SFM). It was used to quantify heterogeneous ice nucleation rate coefficients, mimic the competition between homogeneous ice nucleation; water uptake; deposition ice nucleation and immersion freezing, and predict the T and RHi at which ice was observed. The importance of ferrihydrite to act as a heterogeneous ice nucleating particle in the atmosphere using the SFM is discussed.

High-Stability Cryogenic System for Quantum Computing With Compact Packaged Ion Traps

Cryogenic environments benefit ion trapping experiments by offering lower motional heating rates, collision energies, and an ultrahigh vacuum (UHV) environment for maintaining long ion chains for extended periods of time. Mechanical vibrations caused by compressors in closed-cycle cryostats can introduce relative motion between the ion and the wavefronts of lasers used to manipulate the ions. Here, we present a novel ion trapping system where a commercial low-vibration closed-cycle cryostat is used in a custom monolithic enclosure. We measure mechanical vibrations of the sample stage using an optical interferometer, and observe a root-mean-square relative displacement of 2.4 nm and a peak-to-peak displacement of 17 nm between free-space beams and the trapping location. We packaged a surface ion trap in a cryopackage assembly that enables easy handling while creating a UHV environment for the ions. The trap cryopackage contains activated carbon getter material for enhanced sorption pumping near the trapping location, and source material for ablation loading. Using <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{171}$</tex-math></inline-formula> Yb <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{+}$</tex-math></inline-formula> as our ion, we estimate the operating pressure of the trap as a function of package temperature using phase transitions of zig-zag ion chains as a probe. We measured the radial mode heating rate of a single ion to be 13 quanta/s on average. The Ramsey coherence measurements yield 330-ms coherence time for counter-propagating Raman carrier transitions using a 355-nm mode-locked pulse laser, demonstrating the high optical stability.

Conceptual design of open source IoT based software solution for Cryogenic experiments

Conceptual design of open source IoT based software solution for Cryogenic experiments

Bolometric Double Beta Decay Experiments: Review and Prospects

This review aims to cover the history and recent developments on cryogenic bolometers for neutrinoless double beta decay (0ν2β) searches. A 0ν2β decay observation would confirm the total lepton charge non-conservation, which is related to a global U(1)LC symmetry. This discovery would also provide essential information on neutrino masses and nature, opening the door to new physics beyond the Standard Model. The bolometric technology shows good prospects for future ton-scale experiments that aim to fully investigate the inverted ordering region of neutrino masses. The big advantage of bolometers is the high energy resolution and the possibility of particle identification, as well as various methods of additional background rejection. The CUORE experiment has proved the feasibility of ton-scale cryogenic experiments, setting the most stringent limit on 130Te 0ν2β decay. Two CUPID demonstrators (CUPID-0 and CUPID-Mo) have set the most stringent limits on 82Se and 100Mo isotopes, respectively, with compatibly low exposures. Several experiments are developing new methods to improve the background in the region of interest with bolometric detectors. CUPID and AMoRE experiments aim to cover the inverted hierarchy region, using scintillating bolometers with hundreds of kg of 100Mo. We review all of these efforts here, with a focus on the different types of radioactive background and the measures put in place to mitigate them.

Heat and mass transfer in a cryogenic tank in case of active-pressurization

Predicting the pressurant requirements is one of the key challenges for cryogenic propulsion systems. In this context, a numerical model to simulate the tank pressurization that considers evaporation and condensation phenomena was developed and applied. The novel solver combines a gradient-based phase change model with a weakly compressible multiphase solver of OpenFOAM based on the pressure implicit method with splitting of operator (PISO) algorithm. To maintain a sharp interface the mass source terms are applied to the cells adjacent to the interface. First, the model is validated against two analytical solutions: the one-dimensional phase change problem and secondly, the growth of a vapor bubble in a superheated liquid in the absence of gravity. In a second step, the validated model was applied to a cryogenic pressurization experiment. The measured pressure behavior could be confirmed with the numerical model being in a good approximation. With the numerical model further insights into the physical behavior could be achieved. The condensation and evaporation effects have a significant impact on the pressure development during and after the pressurization. The mass flows due to phase change occurring at the vapor-liquid interface depend on interface location and time. Directly at the wall, evaporation becomes dominant while condensation occurs at the center area of the liquid surface.

Dual-pace transient heat conduction in vertically aligned carbon nanotube arrays induced by structure separation

Vertically aligned arrays of carbon nanotubes (CNTs) are attractive for a wide range of macroscopic applications which can exploit the remarkable properties of individual nanotubes. In this work, an abnormal behavior of CNT bundles in heat conduction is discovered under the transient electro-thermal characterization. The measured voltage change over the sample shows a dual-pace thermal response (DTR), which could not be fitted using a single thermal diffusivity heat transfer model. Instead, two thermal diffusivities are determined from the DTR phenomenon. Three rounds of cryogenic experiments are conducted to investigate the physics behind DTR phenomenon. It starts to emerge when the temperature is reduced to a certain level. After two rounds of cryogenic experiments, the DTR phenomenon becomes permanent from 295 K to 10 K. The nano-scale structure separation induced by the increased thermal strain leads to macroscale structure separation, which results in two parallel heat conduction paths responsible for the DTR phenomenon. By building a new parallel heat transfer model taking both the transient and steady-state electrical and thermal response into consideration, the area ratio of separated CNTs is determined. This result uncovers the existence of coiled morphology and nano-structure evolution of CNTs under cryogenic state and its effect on thermal and electrical transport, especially on their transient behaviors. Knowledge of the thermal transport in these CNTs arrays is important considering the fact that transient thermal response strongly affects their mechanical, optical, and electrical behaviors.

Constraints on Lightly Ionizing Particles from CDMSlite.

The Cryogenic Dark Matter Search low ionization threshold experiment (CDMSlite) achieved efficient detection of very small recoil energies in its germanium target, resulting in sensitivity to lightly ionizing particles (LIPs) in a previously unexplored region of charge, mass, and velocity parameter space. We report first direct-detection limits calculated using the optimum interval method on the vertical intensity of cosmogenically produced LIPs with an electric charge smaller than e/(3×10^{5}), as well as the strongest limits for charge ≤e/160, with a minimum vertical intensity of 1.36×10^{-7} cm^{-2} s^{-1} sr^{-1} at charge e/160. These results apply over a wide range of LIP masses (5 MeV/c^{2} to 100 TeV/c^{2}) and cover a wide range of βγ values (0.1-10^{6}), thus excluding nonrelativistic LIPs with βγ as small as 0.1 for the first time.

Surface Layer Modification by Cryogenic Burnishing of Al 7050-T7451 Alloy With Near Ultra-Fine Grained Structure

Abstract Burnishing has been increasingly utilized to improve the surface integrity of manufactured components. The generation of surface and subsurface layers with ultrafine grains, attributed to severe plastic deformation (SPD) and dynamic recrystallization (DRX), leads to improved surface integrity characteristics including surface and subsurface hardness and reduction in surface roughness. Additionally, due to the generation of compressive stresses within the refined layers, increase in fatigue life and improved wear and corrosion resistance can be achieved. In this study, we apply cryogenic burnishing on Al 7050-T7451 discs and compare the surface integrity characteristics with dry conventional burnishing. A special roller burnishing tool with flexible rotating roller head was designed and used to perform the cryogenic burnishing experiments using liquid nitrogen as the coolant. The results show that cryogenic burnishing can increase the surface hardness by an average of 20–30% within a layer depth of 200 µm compared with only 5–10% increase using dry conventional burnishing. Refined layers with nano grain structure were also generated. During cryogenic burnishing, the tangential burnishing forces were higher than those of dry conventional burnishing due to rapid cooling and work hardening of the material.

Experimental investigation of snow drifting on flat roofs during snowfall: Impact of roof span and snowfall intensity

Owing to the controllability and reliability, wind tunnel experiment is considered as a powerful and effective approach for the investigation of snow drifting. Most of the previous experimental studies were mainly concerned with snow drifting on roofs without snowfall, in which a layer of particles was uniformly paved on the roof surface to model the initial snow cover. Hence, a cryogenic wind tunnel experiment using artificial snow particles was conducted to investigate snow drifting on flat roofs during snowfall. The similarity requirement related to snowfall intensity is derived according to the similarities of snow distribution pattern and the development of snow transport. Based on the results of snow distributions and transport rates for different roof spans and snowfall intensities, the features of snow drifting under snowfall conditions are analyzed in detail. The concurrence of snowfall is further revealed to greatly affect the development of snow drifting on flat roofs and thereby result in a reduction in the required fetch for reaching the saturated state. And the typical distribution patterns for snow drifting on flat roofs with and without snowfall are also summarized. Besides, the snow transport rate is found to increase along the roof surface before the achievement of the saturated state, whereas a slight decrease in the degree of snow erosion with roof span is observed. But the location of the crest formed near the windward edge is nearly unaffected by roof span as well as snowfall intensity. The results also indicate obvious linear characteristics in the relationship between the degree of erosion on the roof surface and snowfall intensity. And the normalized development process of snow transport before reaching the saturated state is nearly independent of snowfall intensity, although both the saturated transport rate and the required fetch for saturated drifting are strongly affected in the meantime.

Inverse ray tracing on icosahedral tetrahedron grids for non-linear laser plasma interaction coupled to 3D radiation hydrodynamics

A novel approach to efficiently model 3-D laser plasma interactions at fluid scales is presented. This method, implemented in the IFRIIT propagation code developed at CELIA, relies on inverse ray tracing to compute laser fields at arbitrary locations in a plasma. This enables to describe the fields at high order in space compared to standard forward ray tracing approaches. In addition, inverse ray tracing enables the use of etalon integral methods to reconstruct caustic fields and greatly speeds up calculations of cross-beam energy transfer by decoupling the ray amplitude and ray phase calculations. A comparison of the inverse and forward methods for 3-D calculations of fields in presence or not of cross-beam energy transfer illustrates the significant advantages of the inverse method. Conversely, while the inverse method is well suited to most spherical plasma profiles, it currently cannot treat concave profiles or target holders. The coupling of IFRIIT with the 3-D ASTER radiative hydrodynamics code developed at the Laboratory for Laser Energetics is then presented. ASTER and IFRIIT resolve their respective equations on separate grids which communicate through interpolation. As such, IFRIIT uses a dedicated laser grid adapted to the computations at play, which also allows to use different parallelization methods for both codes: block decomposition for the hydrodynamics versus domain duplication for the laser. Applications to direct-drive implosions for inertial confinement fusion are presented, for which a geodesic icosahedron grid is implemented in IFRIIT. The performances of the ASTER/IFRIIT coupling are demonstrated by conducting simulations of cryogenic implosions performed on the OMEGA laser system, in presence of various sources of 3-D effects; laser port geometry, cross-beam energy transfer, beam imbalance and target mis-alignment. Comparison with neutron data, measured through bang-time, for a cryogenic implosion experiment shows an excellent agreement for the laser-plasma coupling.

Influence of different thermal evolution stages on shale pore development

ABSTRACT Different thermal evolution degrees on pore development were studied by cryogenic nitrogen adsorption experiment and microscopic photometric analysis. The organic matter Ro, the pore volume, and the proportion of different pore types are different in the Qingshankou Formation, Longmaxi Formation, and Niutitang Formation. However, the relationship between pore development and thermal evolution is consistent. With increasing the degree of the thermal evolution of organic matter holes appear three different change rules. When the organic matter Ro is less than 1.2, shale porosity is mainly influenced by physical compaction and cementation, shale organic hole filling. With the increase of Ro, the porosity tends to decrease, and when Ro is between 1.2 and 3.0, the organic matter of pyrolysis hydrocarbon generation and organic matter hydrocarbon generation hole and corrosion hole a lot of development, the stage total shale porosity is lower before the rising trend, organic matter porosity increased with the increase of Ro. When Ro is greater than 3.0 (overmaturity stage), graphitization occurs. Under the influence of deep burial and slow compaction, the porosity is decreasing continuously.

Maximum shear stress-controlled uniaxial tensile deformation and fracture mechanisms and constitutive relations of Sn–Pb eutectic alloy at cryogenic temperatures

Sn–Pb eutectic alloy is widely applied to the deep-space electronics that work under cryogenic environments, but little is known about its responses to the mechanical loading at cryogenic temperatures. In this work, a comprehensive investigation about the deformation and fracture behaviors as well as constitutive relations of the eutectic alloy at cryogenic temperatures was conducted through uniaxial tensile experiments over a full temperature range from 293 K to 77 K, in-situ cryogenic tensile experiments and fractography. With the declining temperature, the tensile strength and quasi-static toughness increase substantially while the elongation is maintained at 25%–30%; Sn–Pb eutectic alloy achieves the optimal combinations of strength, ductility and toughness at 123 K, which is due to a number of deformation twins activated in the Sn matrix together with the compatible deformation between the Pb-rich phases and the Sn matrix. Multiple 45° shear bands induced by the maximum shear stress contribute to reconcile the deformation difference between the two phases, which reaches its minimum at around 123 K. A ductile shear fracture on the 45° shear planes with respect to the tensile axis occurs under the maximum shear stress at temperatures ranging from 293 K to 123 K, while the maximum normal stress leads to a brittle fracture on the 90° planes at 77 K. Moreover, the Anand model fails in fitting the constitutive relations of Sn–Pb eutectic alloy when the temperature declines to 233 K or lower. Instead, the Hollomon equation has been successfully applied to fit the constitutive relations at these invalid temperatures.

Structure of the superconducting high-pressure phase of Sc3CoC4

We investigate pressure-induced structural changes to the Peierls-type distorted low-temperature phase of the low-dimensional ${\mathrm{Sc}}_{3}\mathrm{Co}{\mathrm{C}}_{4}$ as a possible origin of its pressure-enhanced superconductivity. By means of cryogenic high-pressure x-ray diffraction experiments we could reveal subtle, but significant structural differences between the low-temperature phase at ambient and elevated pressures. We could thus establish the structure of the superconducting phase of the title compound, which interestingly still shows the main features of the Peierls-type distorted low-temperature phase. This indicates that in contrast to other low-dimensional materials a suppression of periodic structural distortions is no prerequisite for superconductivity in the transition-metal carbide.

Comprehensive Regulation of the Threshold Oscillation for Neuromorphic Systems Based on Cryogenic Performance of NbO₂ Device

In this study, an oscillating neuron based on the Pt/ NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> / TiN device with high performance was demonstrated. The temperature dependence of NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> threshold switching devices were well studied at cryogenic environment (100 K), where the reaction intensity is cut down and thus facilitates the observation of the performance and mechanisms of the device. To lucubrate these results, the thermoelectric coupling model was simulatively realized and validated based on cryogenic electrical experiments, guiding the influence factors of NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based oscillation system. Ulteriorly, the NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> threshold switching device as oscillating neuron was simulated and its comprehensive regulation was presented. Ambient temperature, switching time and threshold voltage are found to affect the oscillation frequency, while threshold voltage can also change the amplitude of the frequency affected by other factors. This work performs a systematically cryogenic study of NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and oscillation system, and simultaneously provides a deep understanding of performance regulation mode of the oscillating system.

Application of an energy-dependent instrument response function to analysis of nTOF data from cryogenic DT experiments

Neutron time-of-flight (nTOF) detectors are used to diagnose the conditions present in inertial confinement fusion (ICF) experiments and basic laboratory physics experiments performed on an ICF platform. The instrument response function (IRF) of these detectors is constructed by convolution of two components: an x-ray IRF and a neutron interaction response. The shape of the neutron interaction response varies with incident neutron energy, changing the shape of the total IRF. Analyses of nTOF data that span a broad range of energies must account for this energy-dependence in order to accurately infer plasma parameters and nuclear properties in ICF experiments. This work briefly reviews a matrix multiplication approach to convolution, which allows for an energy-dependent change in the shape of the IRF. This method is applied to synthetic data resembling symmetric cryogenic DT implosions to examine the effect of the energy-dependent IRF on the inferred areal density. The results of forward fits that infer ion temperatures and areal densities from nTOF data collected during cryogenic DT experiments on OMEGA are also discussed.

Infrared matrix-isolation and theoretical studies of interactions between CH3I and water

Gaseous iodomethane are naturally emitted in the atmosphere over oceans through the algae and phytoplankton activities. The fate of naturally emitted iodomethane is of great interest because of the oxidizing properties of iodine in the atmosphere and its impact on the catalytic destruction of the ozone layer. Additionally, iodomethane is one of the gaseous species that can be emitted in the case of severe nuclear accident. The radiological impact of gaseous iodomethane is of concerns and requires knowledge about its behavior in the atmosphere. Water is one of the major species in the atmosphere which is responsible for atmospheric aerosol nucleation and thus, for cloud condensation nuclei (CCN). The fundamental knowledge concerning the interaction between methyl iodine and water at the molecular scale contributes to the better understanding of the fate of such species into the atmosphere and their role in CCN formation. Here the microhydration of iodomethane was investigated using cryogenic matrix experiments which were supported by theoretical DFT calculations. A large excess of water regarding CH3I was used in order to mimic atmospheric conditions. Dimers and trimers of CH3I are observed despite the high water amount in the initial mixture together with hetero aggregates between CH3I and water clusters. This may be explained by the low affinity of CH3I with water. Considering the concentration of iodomethane used in our experiments, the aggregates are rather formed in gas phase and not in the matrix cage. The interaction between CH3I and H2O molecules studied experimentally and supported by DFT calculation highlights that, in the atmosphere, gaseous iodomethane and water will likely form association between water and iodomethane aggregates instead of (CH3I)n-(H2O)m hetero complexes. Our results have important consequences for the understanding of the alkyl halide solvation in primary processes and contribute to the understanding of reactive halogen species in tropospheric chemistry. In the context of a nuclear severe accident, our work is contributing to better understand the fate of nuclear species in the atmosphere and thus, the radionuclide dispersion.

Structural Insights from Tandem Mass Spectrometry, Ion Mobility-Mass Spectrometry, and Infrared/Ultraviolet Spectroscopy on Sphingonodin I: Lasso vs Branched-Cyclic Topoisomers.

Lasso peptides form a class of ribosomally synthesized and post-translationally modified peptides (RiPPs) characterized by a mechanically interlocked topology, where the C-terminal tail of the peptide is threaded and trapped within an N-terminal macrolactam ring. Sphingonodin I is a lasso peptide that has not yet been structurally characterized using the traditional structural biology tools (e.g., NMR and X-ray crystallography), and its biological function has not yet been elucidated. In the present work, we describe structural signatures characteristic of the class II lasso peptide sphingonodin I and its branched-cyclic analogue using a combination of gas-phase ion tools (e.g., tandem mass spectrometry, MS/MS, trapped ion mobility spectrometry, TIMS, and infrared, IR, and ultraviolet, UV, spectroscopies). Tandem MS/MS CID experiments on sphingonodin I yielded mechanically interlocked species with associated bi and yj fragments demonstrating the presence of a lasso topology, while tandem MS/MS ECD experiments on sphingonodin I showed a significant increase in hydrogen migration in the loop region when compared to the branched-cyclic analogue. The high-mobility resolving power of TIMS permitted the separation of both topoisomers, where sphingonodin I adopted a more compact structure than its branched-cyclic analogue. Cryogenic and room-temperature IR spectroscopy experiments evidenced a different hydrogen bond network between the two topologies, while cryogenic UV spectroscopy experiments clearly demonstrated a distinct phenylalanine environment for the lasso peptide.