Dominant Mechanism Research Articles

Abstract SY07-01: p53-mediated stem cell competition: Insights into mechanisms of clonal dominance

Abstract TP53 Mutations confer clonal advantage in several tissues contributing to tumorigenesis. It has traditionally been proposed that heightened resistance to apoptosis/cell cycle arrest can account for clonal advantage. P53 mediated clonal dominance has also been observed in cultured embryonic stem (ES) cells, though it is not clear how this is established. Using live cell imaging we show that human ES cells (hESCs) mutant for TP53 induce death of hES-WT cells and outcompete them. Competition is mediated by apoptosis induction and requires direct cell contact, as in co-cultures of hES-P53KO and hES-WT cells where contact is prevented competition is not observed. To ask if hES-P53KO competition is mediated by mechanical interactions, we cultured cells on deformable membranes to measure their resistance to cell compaction. Interestingly, while hES-WT cells displayed apoptosis induction upon cell compaction, hES-P53KO cells were resistant to compaction-induced apoptosis. We suggest that differential sensitivity to compaction in crowded cultures/tissues can drive p53-induced competitive cell elimination. Identifying the mechanisms by which p53 confers resistance to cell compaction could lead to novel actionable targets to prevent the expansion of p53 mutant stem cells in cancerous and pre-cancerous lesions. Citation Format: Eugenia Piddini. p53-mediated stem cell competition: Insights into mechanisms of clonal dominance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr SY07-01.

Interannual Lightning Variability within the TRMM LIS Dataset Using an ENSO Perspective

Abstract The Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) was used to investigate interannual variability of lightning from 1998 to 2014 within the 38°S–38°N range. Previous studies have indicated that the El Niño–Southern Oscillation (ENSO) phenomenon is one significant contributor to interannual lightning variability, potentially the dominant mechanism on the global scale. This period of 16 years contained four warm- (El Niño), eight cold- (La Niña), and four neutral-phase ENSO years based on the oceanic Niño index. Large magnitude lightning anomalies were found during the warm phase of ENSO, with mean warm-phase anomalies of >10 flashes (1000 km)−2 min−1 in north-central Africa and Argentina. This includes a +35 flashes (1000 km)−2 min−1 anomaly in Argentina during the 2009 El Niño. In general, large-scale anomalies of thermodynamic properties and upper-atmospheric vertical motion coincided with the lightning anomalies observed in both Africa and South America. The anomaly over north-central Africa, however, was characterized by a 6-week shift in the annual lightning maximum with the warm phase, a result of the more complex environmental response to ENSO over the Sahel. The most consistent ENSO anomalies with appreciable lightning were found in southeastern Africa, northwestern Brazil, central Mexico, and the southern Red Sea. Of these, all but the Mexico region had enhanced lightning with the cold phase and suppressed lightning with the warm phase.

Moiré Pattern Controlled Phonon Polarizer Based on Twisted Graphene.

Twisted van der Waals materials featuring Moiré patterns present new design possibilities and demonstrate unconventional behaviors in electrical, optical, spintronic, and superconducting properties. However, experimental exploration of thermal transport across Moiré patterns has not been as extensive, despite its critical role in nanoelectronics, thermal management, and energy technologies. Here, thefirst experimental study is conducted on thermal transport across twisted graphene, demonstrating a phonon polarizer concept from the rotational misalignment between stacked layers. The direct thermal and acoustic measurements,structural characterizations, and atomistic modeling, reveal a modulation up to 631% in thermal conductance with various Moiré angles, while maintaining a high acoustic transmission. By comparing experiments with density functional theory and molecular dynamics simulations, mode-dependent phonon transmissions are quantified based on the angle alignment of graphene band structures and attributed to the coupling among flexural phonon modes. The agreement confirms the dominant tuning mechanisms in adjusting phonon transmission from high-frequency thermal modes while having negligible effects on low-frequency acoustic modes near Brillouin zone center. This study offers crucial insights into the fundamental thermal transport in Moiré structures, opening avenues for the invention of quantum thermal devices and new design methodologies based on manipulations of vibrational band structures and phonon spectra.

Sublithospheric diamonds extend Paleoproterozoic record of cold deep subduction into the lower mantle

Cold deep subduction – a hallmark of modern-style plate tectonics – is the dominant mechanism for recycling crustal materials into Earth's deep mantle, potentially changing its composition, heat budget and dynamics. The onset of cold deep subduction remains contentious and is largely constrained by crustal rocks, despite subduction being driven by mantle processes. Here we use the chemical and chronological information from sublithospheric mantle-derived minerals entrapped in diamonds from the DO-27 kimberlite, Slave Craton, Canada, to better constrain the timing and products of cold deep subduction reaching Earth's lower mantle. DO-27 sublithospheric diamonds preserve a complete lower mantle mineral assemblage: Ca-silicates (retrogressed CaSi-perovskite) ± enstatite (retrogressed bridgmanite) ± ferropericlase. The high Mg#s (molar Mg/(Mg+Fe)) of retrogressed bridgmanite (median Mg#=95) and ferropericlase (median Mg#=86) implicate a harzburgitic host rock for the diamonds. This strongly melt-depleted signature contrasts with the high abundance of Ca-silicate inclusions, some of which are variably enriched in incompatible elements and have enriched Sr-Nd-Pb isotopic signatures that collectively indicate the host rock was metasomatized by carbonatitic melts released from a relatively cold subducting slab in the lower mantle. The U-Pb systematics of the Ca-silicates define two ages of diamond crystallisation: 998 ± 18 Ma and 1679 ± 13 Ma. This is the first direct evidence of cold deep subduction in Earth's lower mantle at ∼1.7 Ga (Paleoproterozoic), in agreement with the oldest crustal low-temperature, high-pressure eclogites and is much earlier than previous Neoproterozoic estimates.

Metallurgical and Mechanical Properties of Friction Stir-Welded Pure Titanium

AbstractCommercially pure titanium (CP-Ti) plates were friction stir welded (FSWed) using a welding tool with a tungsten carbide (WC) pin. The bead-on-plate technique was applied to reduce the effects of welding defects, such as incomplete penetration. Whereas many papers have reported on creep studies of CP-Ti as well as on FSW of CP-Ti, no paper has investigated the creep behavior of a CP-Ti FSW’ed joint. Consequently, the current study focuses on this topic. The current paper, which is part of a broader research project, focuses on the metallurgical processes occurring during the creep of a FSW’ed CP-Ti joint at the temperature range of 550-650 °C. Based on the current study and previous results obtained by the authors, it can be concluded that the weld is not the weakest link. In every case, necking and creep fracture occurred in the parent material (PM), rather than either the thermomechanically affected zone (TMAZ) or the stir zone (SZ), indicating that both zones are more creep-resistant than the parent material. Fractography showed that the fracture surface was typical of creep fracture and that the fracture mechanism was microvoid coalescence and also ruled out any preexisting defect. TEM study of broken crept specimens revealed randomly distributed dislocations but no evidence of grain refinement, hence leading to the conclusion that dislocation glide was the dominant creep mechanism. The technological implication of the current study is that the welding process is safe for use as far as its creep properties are concerned.

Emission of Parasitic X Rays of Vacuum-electron Tubes with Glass Housings: Implications for the Evaluation of Occupational Doses.

Despite the large variety of high-voltage semiconductor components for medium and high voltage switching and pulse-forming applications as well as for high-power high-frequency generation, the use of vacuum electron tubes still prevails to a considerable degree. Due to the common design incorporating a high energy electron beam which finally is dumped into an anode or a resonator cavity, these tubes are also considered as sources of X rays produced as bremsstrahlung and characteristic radiation, which are referred to as parasitic X rays. Here three types of vacuum-electron tubes, diode, tetrode, and thyratron, with glass housings are investigated. They are predominantly operated in the high voltage range below 30 kV and are not subject to licensing laws. The measurements of the dose rate and X-ray-spectra were performed in the laboratory without complex electrical circuitry usually used in making practical measurements for occupational radiation protection. For the diode tube, where a parasitic X-ray emission is observed only in the reverse operation as a blocking diode, a broad distribution of dose rates of electrically equivalent specimens was observed. This is attributed to field emission from the electrodes. For the tetrode and the thyratron tubes, field emission from the electrodes is identified as the dominant mechanism for the generation of parasitic X rays. Thus, technical radiation protection must focus on shielding of the glass tube rather than optimization of the electrical circuitry.

Stability analysis of WEST L-mode discharges with improved confinement from boron powder injection

WEST L-mode plasmas with dominant electron heating and no core torque source have observed improvements in confinement during boron (B) powder injection. These results are reminiscent of previous powder injection experiments on other devices and gaseous impurity seeding experiments on WEST. During powder injection, the stored energy increased up to 25% due to enhanced ion and electron heat and particle confinement. The improvements in confinement were not indicative of an L-H transition. To identify the dominant mechanisms and the causality chain behind these improvements in confinement, we employ interpretative modeling using METIS, predictive integrated modeling using a high-fidelity plasma simulator (HFPS), and stand-alone gyrokinetic simulations using quasi-linear gyrokinetic code. Interpretative modeling with METIS allowed for the estimation of missing data while maintaining good overall consistency with experiment. These results provided the initial conditions for fully predictive flux driven simulations using the HFPS. From these simulations, quasi-linear gyrokinetic analysis was performed at ρ=0.5 and ρ=0.65 . Collisionality was found to be a strong candidate for the turbulence suppression mechanism at ρ=0.5 , while a combination of collisionality and the Te/Ti ratio was found to be the likely mechanism at ρ=0.65 . The results additionally suggested that increased Zeff (through main ion dilution) could play a role in the improved confinement, but this could not be confirmed due to a lack of experimental measurements. The modeling framework established here can now be used to evaluate and exploit a variety of future powder injection experiments.

Neoproterozoic Lysan Alkaline–Ultramafic Complex in the Eastern Sayan, Southern Siberia, Russia: Mineralogical Constraints of Carbonate Rocks and Albitite for Petrogenesis

The Lysan alkaline–ultramafic complex is located in the Sisim shear zone at the contact of the two largest tectonic structures of the accretion–collisional belt in the southwestern frame of the Siberian craton. Intrusions of the complex consist of ore-bearing olivinites, kaersutite clinopyroxenites, and banded kaersutite gabbro, which have been «cut» by albitite dykes and veins. The veins and veinlets of the carbonate rocks are mainly associated with the albitites. The present paper represents the first detailed mineralogical study of carbonate rocks and albitites in the Podlysansky Massif of the Neoproterozoic Lysan alkaline–ultramafic complex. The mineral composition was determined in situ in a polished section by scanning electron microscopy, energy dispersive spectrometry, and electron probe microanalysis. The carbonate rocks of the Podlysan Massif have been found to contain minerals that are typical of siderite–carbonatites (senso stricto), including calcite, siderite, phengitic muscovite, apatite, monazite, REE fluorocarbonates, pyrite, and sphalerite. These rocks are enriched in light rare earth elements due to the presence of monazite-(Ce), bastnäsite-(Ce), parisite-(Ce), and synchysite-(Ce). The albitites were formed as a result of the fenitization of leucocratic gabbro by alkali-rich carbo-hydrothermal fluids in zones of intense development of tectonic fractures. Infiltration was the dominant mechanism of fenitization. The obtained data significantly enhance the current understanding of the geochemical and ore specialization of rocks in the Lysan Complex.

Model construction and dominant mechanism analysis of li-ion batteries under periodic excitation

Model construction and dominant mechanism analysis of li-ion batteries under periodic excitation

Dynamic Reconstruction of Two-Dimensional Defective Bi Nanosheets for Efficient Electrocatalytic Urea Synthesis.

Catalyst surface dynamics drive the generation of active species for electrocatalytic reactions. Yet, the understanding of dominant site formation and reaction mechanisms is limited. In this study, we thoroughly investigate the dynamic reconstruction of two-dimensional defective Bi nanosheets from exfoliated Bi2Se3 nanosheets under electrochemical CO2 and nitrate (NO3 -) reduction conditions. The ultrathin Bi2Se3 nanosheets obtained by NaBH4-assisted cryo-mediated liquid-phase exfoliation are more easily reduced and reconstructed to Bi nanosheets with high-density grain boundaries (GBs; GB-rich Bi). The reconstructed GB-rich Bi catalyst affords a remarkable yield rate of 4.6 mmol h-1 mgcat. -1 and Faradaic efficiency of 32 % for urea production at -0.40 V vs. RHE. Notably, this yield rate is 2 and 8.2 times higher than those of the low-GB Bi and bulk Bi catalysts, respectively. Theoretical analysis demonstrates that the GB sites significantly reduce the *CO and *NH2 intermediate formation energy and C-N coupling energy barrier, enabling selective urea electrosynthesis on the GB-rich Bi catalyst. This work will trigger further research into the structure-activity interplay in dynamic processes using in situ techniques.

Study the Efficiency of the XGBoost Algorithm for Squat RC Wall Shear Strength Prediction and Parametric Analysis

Squat-reinforced concrete (RC) shear walls with an aspect ratio of less than two are considered effective structural members, where shear is the dominant failure mechanism. Squat shear walls are widely used in nuclear power plants and building construction and feature optimal cost and outstanding performance, due to their lateral strength and high rigidity to resist lateral loads. However, since the accurate evaluation of the shear strength of squat shear walls must meet the design specifications, its calculation may be very complex, challenging, and inaccurate using experimental and theoretical equations due to many influential and overlapping design factors, so it takes more time and higher cost to determine it. This study uses machine learning (ML) methods to build a shear strength prediction efficient model for squat RC walls to address these issues. First, a huge dataset of 1424 RC squat wall test specimens gathered from the literature is utilized for developing an ML model, by employing XGBoost, to predict the shear strength. Results verified that the XGBoost model had the best accuracy and least error while assessing the squat walls' strength at shear. Moreover, an XGBoost optimum algorithm fared better than the empirical models based on mechanics, with a 99.2% accuracy. Finally, to prove that the model can identify the most important variables that significantly affect the shear strength, parameter and sensitivity analyses were performed and the results showed that the wall length is the factor that contributes most to the ultimate shear strength of the squat shear wall as a percentage (7.62%), followed by the yield strength. For the web as a ratio. (6.88%), concrete strength (6.75%), reinforcement ratio information (6.56%), and geometric properties (6.01%), while the axial load represents the smallest contribution, reaching (4.16%).

Trap-Mediated Sensitization Governs Near-Infrared Emission from Yb3+-Doped Mixed-Halide CsPbClxBr3-x Perovskite Nanocrystals.

Understanding the photosensitization mechanisms in Yb3+-doped perovskite nanocrystals is crucial for developing their anticipated photonic applications. Here, we address this question by investigating near-infrared photoluminescence of Yb3+-doped mixed-halide CsPbClxBr3-x nanocrystals as a function of temperature and revealing its strong dependence on the stoichiometry of the host perovskite matrix. To explain the observed experimental trends, we developed a theoretical model in which energy transfer from the perovskite matrix to Yb3+ ions occurs through intermediate trap states situated beneath the conduction band of the host. The developed model provides an excellent agreement with experimental results and is further validated through the measurements of emission saturation at high excitation powers and near-infrared photoluminescence quantum yield as a function of the anion composition. Our findings establish trap-mediated energy transfer as a dominant photosensitization mechanism in Yb3+-doped CsPbClxBr3-x nanocrystals and open up new ways of engineering their optical properties for light-emitting and light-harvesting applications.

Dynamic Reconstruction of Two‐Dimensional Defective Bi Nanosheets for Efficient Electrocatalytic Urea Synthesis

AbstractAbstract:Catalyst surface dynamics drive the generation of active species for electrocatalytic reactions. Yet, the understanding of dominant site formation and reaction mechanisms is limited. In this study, we thoroughly investigate the dynamic reconstruction of two‐dimensional defective Bi nanosheets from exfoliated Bi2Se3 nanosheets under electrochemical CO2 and nitrate (NO3−) reduction conditions. The ultrathin Bi2Se3 nanosheets obtained by NaBH4‐assisted cryo‐mediated liquid‐phase exfoliation are more easily reduced and reconstructed to Bi nanosheets with high‐density grain boundaries (GBs; GB‐rich Bi). The reconstructed GB‐rich Bi catalyst affords a remarkable yield rate of 4.6 mmol h−1 mgcat.−1 and Faradaic efficiency of 32 % for urea production at −0.40 V vs. RHE. Notably, this yield rate is 2 and 8.2 times higher than those of the low‐GB Bi and bulk Bi catalysts, respectively. Theoretical analysis demonstrates that the GB sites significantly reduce the *CO and *NH2 intermediate formation energy and C−N coupling energy barrier, enabling selective urea electrosynthesis on the GB‐rich Bi catalyst. This work will trigger further research into the structure‐activity interplay in dynamic processes using in situ techniques.

Passive Biotelemetric Detection of Tibial Debonding in Wireless Battery-Free Smart Knee Implants.

Aseptic loosening is the dominant failure mechanism in contemporary knee replacement surgery, but diagnostic techniques are poorly sensitive to the early stages of loosening and poorly specific in delineating aseptic cases from infections. Smart implants have been proposed as a solution, but incorporating components for sensing, powering, processing, and communication increases device cost, size, and risk; hence, minimising onboard instrumentation is desirable. In this study, two wireless, battery-free smart implants were developed that used passive biotelemetry to measure fixation at the implant-cement interface of the tibial components. The sensing system comprised of a piezoelectric transducer and coil, with the transducer affixed to the superior surface of the tibial trays of both partial (PKR) and total knee replacement (TKR) systems. Fixation was measured via pulse-echo responses elicited via a three-coil inductive link. The instrumented systems could detect loss of fixation when the implants were partially debonded (+7.1% PKA, +32.6% TKA, both p < 0.001) and fully debonded in situ (+6.3% PKA, +32.5% TKA, both p < 0.001). Measurements were robust to variations in positioning of the external reader, soft tissue, and the femoral component. With low cost and small form factor, the smart implant concept could be adopted for clinical use, particularly for generating an understanding of uncertain aseptic loosening mechanisms.

Effects of boron doping in InSe single crystals on optical limiting performance in the near-infrared region

Identification of photonic materials with high infrared transmittance and high nonlinear optical coefficients is one of the main emphases in material science as a result of the rapid advancement in infrared photonics. In this study, undoped and B (boron) -doped InSe single crystals were grown by using the modified vertical Bridgman method, and their nonlinear optical properties were investigated to reveal their usability as an optical limiter in the near-infrared region. The decreasing band gap energies and increasing defect states were determined with increasing B concentration in InSe single crystals. The effect of the B concentration on the nonlinear absorption (NA) and optical limiting properties of the InSe single crystals was investigated via open aperture (OA) Z-scan experiments under ultrafast laser excitation at 1200 nm wavelength with 100 femtosecond pulse duration. Two-photon absorption (TPA) was the dominant NA mechanism at 1200 nm excitation wavelength in the femtosecond domain. The results revealed that the NA became stronger with increasing input intensity and increasing amount of B dopant atoms in the InSe single crystal. The observed enhanced NA can be attributed to two possible events (i) increasing input intensity induced more excited electrons which led to more contribution to NA through TPA and (ii) increasing B dopant atoms in InSe single crystal induced more defect states. The NA may be more enhanced with the contribution of these defect states related NA mechanisms. The high transparency and strong NA behavior at the near-infrared region make these single crystals exceptional potential candidates for developing various optoelectronics and filters at the near-infrared spectral region.

Influence of the substrate conductivity type on the electroluminescence properties of PP+IN and PIN+N diodes based on amorphous silicon carbide (a-Si1-xCx:H) / crystalline silicon (c-Si) heterostructures

The study of the conduction and light emission mechanisms of PIN diodes based on amorphous silicon-carbide (a-Si1-xCx:H) thin film and crystalline silicon (c-Si) substrates is reported in this work. Using the same low-temperature process (200 °C), PP+IN and PIN+N structures were fabricated on p-type and n-type silicon (Si) substrates, respectively. The plasma enhanced chemical vapor deposition (PECVD) technique was employed for the active layers deposition where two different CH4/SiH4 flow rates ratios of 30 sccm/6 sccm and 30 sccm/1 sccm were used. All structures show red-orange light emission in forward bias (FB). The structures with the active layer deposited with a lower SiH4 flow rate, display light emission with a higher intensity at a lower voltage bias.In addition, we related the current-voltage measurements with different conduction models and the dominant charge transport mechanisms in the PIN structures were proposed. The highest Si content structures were related to Fowler-Nordheim (F-N) tunneling, because of its active layer with lower barrier height. On the other hand, the lowest Si content structures were associated with the Poole-Frenkel (P-F) emission, due to a higher density of defects in localized tail states. The results showed the same conduction and emission mechanisms for the PP+IN and PIN+N diodes with the same active layer, regardless of the conduction type of substrate, proving that it is feasible to use the same process for developing light emission devices on p-type and n-type Si substrates.

Modulation of Primary and Secondary Processes in Tau Fibril Formation by Salt-Induced Dynamics.

The initial stages of amyloid fibrilization begin with the monomers populating aggregation-prone conformers. Characterization of such aggregation-prone conformers is crucial in the study of neurodegenerative diseases. The current study characterizes the aggregation pathway of two tau protein constructs that have been recently demonstrated to form Alzheimer's (AD) fibril structures with divalent ions and chronic traumatic encephalopathy (CTE) fibril structures with monovalent ions. The results highlight the involvement of identical residues in both the primary and secondary processes of both AD and CTE fibril propagation. Nuclear magnetic resonance relaxation experiments reveal increased flexibility of the motifs 321KCGS within R3 and 364PGGGN within R4 in the presence of MgCl2/NaCl, correlating with faster aggregation kinetics and indicating efficient primary nucleation. Notably, the seeded aggregation kinetics of the tau monomers in the presence and absence of metal ions are strikingly different. This correlates with the overall sign of the 15N-ΔR2 profile specifying the dominant mechanism involved in the process of aggregation.

Jet Mechanism and γ-Ray-emitting Region for Fermi Flat-spectrum Radio Quasars with Broad-line Emissions

Blazars are a subject of intense debate, specifically regarding their jet launch and emission mechanisms, and the origins of their γ-ray radiation. To explore these issues, we have built a comprehensive sample of flat-spectrum radio quasars (FSRQs), with well-characterized spectral energy distribution. This study aims to elucidate the dominant jet launch mechanism and the main processes behind the inverse Compton (IC) component. Additionally, we seek to pinpoint the location of the γ-ray dissipation region relative to the central black hole, denoted as R γ . Our approach involves a detailed analysis of broad-line region (BLR) emission, from which we derive robust estimates of the black hole masses using two distinct virial techniques. This enables us to constrain the jet power across a wide array of FSRQs. Our findings lead to several significant conclusions: (i) The correlation of jet power with black hole mass allows us to test the Blandford–Znajek, Blandford–Payne, and hybrid mechanisms. We find that the hybrid mechanism is most effective in explaining the jet power observed in the majority of FSRQs; (ii) The IC component of the γ-rays in FSRQs is predominantly due to the external Compton process. (iii) Through simulations, we determine the minimum and maximum values of R γ (the γ-ray dissipation region) and conclude it is located outside the BLR. This conclusion is derived from the variability timescale analysis.

Photo-thermoelectric effect-driven detection of optical communication light in graphene/hBN heterostructures

We report on the photodetection properties of high-quality graphene encapsulated by hexagonal boron nitride under illumination with optical communication light. We demonstrate a gate-tunable photocurrent and zero-bias switching cycle operation at RT. Through gate and temperature-dependent photocurrent measurements, we determine that the dominant photoresponse mechanism is the photo-thermoelectric effect. At low temperatures, the photocurrent in finite doping regions correlates with the Seebeck coefficient, while sharp peaks emerge near the charge neutrality point due to an edge-excited photocurrent. Our study provides guidelines for high-performance graphene-based optoelectronic devices.

Cation exchange to montmorillonite induces selective adsorption of amino acids

Concentrating simple organic molecules, such as amino acids, in the adsorbed phase could have been an early step in prebiotic evolution towards more complex bio-macromolecules on the early Earth. Smectite clay minerals represent potential selective sorbents for prebiotic molecules because of their negative structural charge and high surface area. This study evaluated the adsorption behavior of amino acids to montmorillonite, a well-characterized smectite, at varying pH and fluid compositions. At both pH 5 and 7 in a sodium chloride fluid, amino acids with basic sidechains (L-arginine and L-lysine), which are primarily cationic under these conditions, were selectively adsorbed to montmorillonite with Langmuir constants much greater than amino acids that were predominantly zwitterionic or anionic in solution. On average, the Langmuir constants for the cationic amino acids were 30 (pH 5) and 50 (pH 7) times greater than the constants for zwitterionic amino acids and 120 (pH 5) and 80 (pH 7) times greater than the constants for L-glutamic acid. Under the same pH conditions in a magnesium chloride solution, the adsorption of L-arginine and L-lysine was substantially inhibited with Langmuir constants ∼ 10 times smaller. These observations suggest that cation exchange is the dominant adsorption mechanism for amino acids on montmorillonite. X-ray diffraction and infrared spectroscopy indicate that L-arginine and L-lysine enter the smectite interlayer where the protonated amino sidechain has the strongest interactions with the mineral surface, further supporting adsorption driven primarily through electrostatic interactions. Therefore, smectites on the early Earth may have selectively concentrated cationic amino acids, providing a potential template for the polymerization of α-amine linked peptides.