Natural Isotopic Abundance Research Articles

Carbon and nitrogen cycling in a lead polluted grassland evaluated using stable isotopes (\u03b413C and \u03b415N) and microbial, plant and soil parameters

AimsCarbon (C) and nitrogen (N) cycling are key ecosystem functions potentially altered by heavy metal pollution. We used an ecosystem approach to study the long-term effect of lead (Pb) on C and N cycles in a natural grassland in a former shooting range.MethodsMicrobial activity was evaluated by substrate-induced respiration (SIR) in situ, adding isotopically labelled C4-sugar to the soil. C and N contents and natural abundance of isotopes were measured in grass leaves, soil and microbial biomass together with root biomass.ResultsA reduced microbial activity and microbial biomass per area, together with a higher soil C stock and C:N ratio suggested a lower microbial decomposition in high Pb compared to low Pb areas. A more closed N cycle in the high Pb area was indicated by 2–3‰ lower δ15N in leaves and soil compared to low Pb areas. Higher δ13C in leaves and higher root biomass but similar leaf nutrient contents indicated plant responses and adaptions to the high Pb.ConclusionsThe applied ecosystem approach revealed that Pb slowed down the C and N cycles, possibly by indirect effects rather than by direct toxicity. The ecosystem seems to have adapted to altered conditions.

Isotopic evidence of arbuscular mycorrhizal cheating in a grassland gentian species.

All orchids and pyroloids are mycoheterotrophic at least in the early stage. Many species are predisposed to mycoheterotrophic nutrition even in the adult stage, due to the initial mycoheterotrophy during germination. Although other green plants, such as gentian species, also produce numerous minute seeds, whose germination may depend on fungal associations to meet C demands, physiological evidence for partial mycoheterotrophy in the adult stage is lacking for most candidate taxa. Here, we compared the natural abundances of 13C and 15N isotopes in the AM-associated gentian species Pterygocalyx volubilis growing in high-light-intensity habitats with those of co-occurring autotrophic C3 and C4 plants and AM fungal spores. We found that P. volubilis was significantly enriched in 13C compared with the surrounding C3 plants, which suggests the transfer of some C from the surrounding autotrophic plants through shared AM networks. In addition, the intermediate δ15N values of P. volubilis, between those of autotrophic plants and AM fungal spores, provide further evidence for partial mycoheterotrophy in P. volubilis. Although it is often considered that light deficiency selects partial mycoheterotrophy, we show that partial mycoheterotrophy in AM-forming plants can evolve even under light-saturated conditions. The fact that there have been relatively few descriptions of partial mycoheterotrophy in AM plants may not necessarily reflect the rarity of such associations. In conclusion, partial mycoheterotrophy in AM plants may be more common than hitherto believed.

An experimental setup for creating and imaging 4He2 * excimer cluster tracers in superfluid helium-4 via neutron-3He absorption reaction.

For the purpose of future visualization of the flow field in superfluid helium-4, clusters of the triplet state excimer 4He2 * are generated along the micro-scale recoil tracks of the neutron-absorption reaction n + 3He → 3T + p. This reaction is induced by neutron irradiation of the 3He fraction contained in natural isotopic abundance liquid helium with neutron beams either from the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility (JPARC)/Materials and Life Science Experimental Facility or from the Kyoto University Institute for Integrated Radiation and Nuclear Science. These 4He2 * clusters are expected to be ideal tracers of the normal-fluid component in superfluid helium with several advantageous properties. Evidence of the excimer generation is inferred by detection of laser induced fluorescence emitted from the 4He2 * clusters excited by a purpose-built short pulse gain-switched titanium:sapphire (Ti:sa) laser operating at a wavelength of 905 nm. The setup and performance characteristics of the laser system including the Ti:sa and two continuous wave re-pumping lasers are described. Detection at the fluorescence wavelength of 640 nm is performed by using optical bandpass filtered photomultiplier tubes (PMT). Electrical noise in the PMT acquisition traces could successfully be suppressed by post-processing with a simple algorithm. Despite other laser-related backgrounds, the excimer was clearly identified by its fluorescence decay characteristics. Production of the excimer was found to be proportional to the neutron flux, adjusted via insertion of different collimators into the neutron beam. These observations suggest that the apparatus we constructed does function in the expected manner and, therefore, has the potential for groundbreaking turbulence research with superfluid helium.

Isobaric Spike Method for Absolute Isotopic Ratio Determination by MC-ICP-MS.

Absolute isotopic ratios are required for isobaric interference corrections, spike calibrations, and isotopic analysis by external normalization methods. However, high-precision natural isotopic abundance data are lacking for many elements, particularly those with less than four isotopes or having isobaric isotopes with other elements. In this study, we developed a method for absolute isotope ratio analysis, which integrates the concept of the double-spike method with isotopic analysis of element pairs that have isobaric isotopes. Using multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS), the isotopic composition of a sample can be derived by measuring a series of mixtures of the sample and a spike element that has an isobaric isotope with the element being analyzed. We applied this method to five pairs of elements (Ca-Ti, V-Ti, Cr-Ti, Ni-Zn, and In-Sn) and obtained the absolute isotopic ratios for Ca, V, Cr, Ni, and In, as well as the relative Ca isotopic composition. By simultaneous measurement of Ti and Ca isotopes, a quantitative relationship between the instrumental mass fractionation factors and element masses was developed. After correcting for the difference in instrumental mass fractionation factors, the obtained absolute ratios agree well with the literature data and have per mil level accuracy. This method has considerable potential in measuring the absolute isotopic ratios of elements that have isobaric isotope with other elements. Such precisely determined absolute isotopic ratios and the relationship between the instrumental mass fractionation factors and elemental masses will improve isobaric interference corrections, particularly when chemical purification is imperfect or during laser ablation analysis.

A dual natural lithium formate/L-alanine EPR dosimeter for a mixed radiation field in a boron neutron capture therapy irradiation facility

Standard commercial L-alanine pellets and specially prepared natural lithium formate monohydrate powder samples of specific granulometry were irradiated in a 60Co gamma-ray irradiation plant and in the mixed field (thermal neutrons and gamma photons) of a boron neutron capture therapy (BNCT) experimental facility. The γ-doses applied with the 60Co source range from 0.1 to 50 kGy, while those in the BNCT facility go from ~7 Gy to 150 Gy. The thermal neutron fluences range from 1012 neutrons cm−2 to 2 1013 neutrons cm−2. The irradiation of materials promotes the creation of stable electronic defects (generally free radicals) which constitute paramagnetic centers that can be detected and quantified by electron paramagnetic resonance (EPR). After irradiation, the EPR characterization of the samples was performed by determining the EPR intensity of the spectrum relative to a reference standard constituted by Mn2+ impurities diluted into a MgO single crystal. As expected, L-alanine has revealed to be largely insensitive to thermal neutrons fluence in the investigated range. On the contrary, it is shown that the EPR intensity of irradiated natural lithium formate monohydrate powders is clearly sensitive to thermal neutrons and has a linear dependence with the γ-dose. We propose a dual dosimeter by combining L-alanine pellets and formate powders that would allow to determine the γ-dose and thermal neutron fluence in a selected position of the BNCT irradiation facility. Moreover, we demonstrate that the 6Li enrichment that has been proposed in the literature to enhance the performance of lithium-based EPR dosimeters is not crucial in our case. Instead, the natural isotopic abundance of lithium is large enough to obtain a satisfactory sensibility to thermal neutrons in our BNCT facility for fluencies >1012 neutrons cm−2.

Weaning and stunting affect nitrogen and carbon stable isotope natural abundances in the hair of young children

Natural abundances of stable nitrogen and carbon isotopes (δ15N and δ13C) can vary with both dietary intake and metabolic (specifically catabolic) state. In low-income countries, weaning is a period of dietary transition from milk to plant-based foods and a high-risk period for malnutrition. We explored how diet and malnutrition impact hair δ15N and δ13C in young children by an observational, cross-sectional study in Cox’s Bazar District, Bangladesh [255 children, 6–59 months with 19.6% wasted (7.1% severely) and 36% stunted (9.8% severely)]. Hair δ15N and δ13C exhibited exponential decreases with age, with the loss of one trophic level (3.3‰ and 0.8‰, respectively) from 6 to 48 months, which we associate with the shift from exclusive breastfeeding to complete weaning. After adjustment for age and breastfeeding status, hair isotopic values were unaffected by wasting but lower in severe stunting (−0.45‰ to −0.6‰, P < 0.01). In this population of young children, whose isotopic values in hair primarily depended on age, we failed to observe any effect of wasting, likely due to opposite, compensating effects between dietary and metabolic changes involved. In contrast, we evidenced low δ15N and δ13C values in severely stunted children that likely indicate chronic exposure to diets low in animal products.

Mechanisms responsible for N2O emissions from intertidal soils of the Yangtze Estuary.

Estuarine and coastal wetland ecosystems are important sources of atmospheric nitrous oxide (N2O). However, the underlying driver of emitted N2O from estuarine and coastal wetlands remains poorly understood. Here, natural-abundance isotope technique was applied to characterize the processes responsible for N2O emission from the intertidal soils of the Yangtze Estuary. Measured N2O emission rates ranged from 0.70 to 2.15μmolm-2h-1, with relatively high values at the upper estuarine sites. The δ15N, δ18O and SP (intramolecular 15N site preference) of emitted N2O varied from -4.5 to 6.7‰, 42.4 to 53.2‰, and 6.7 to 15.4‰, respectively. Gross N2O production and consumption rates were within the ranges of 3.16-14.34μmolm-2h-1 and 2.22-12.54μmolm-2h-1, respectively, showing a similar spatial pattern to N2O emission. N2O consumption proportion varied from 69.56 to 90.31%, which was generally lower at the upper estuarine sites. The gross production rates and consumption degree of N2O simultaneously controlled the variations in N2O emission. Bacterial denitrification was the dominant production pathway (78.22-97.36%), while hydroxylamine (NH2OH) oxidation contributed 2.64-21.78% to N2O production. Soil pH, Fe2+/Fe3+, sulfide and substrate availability were probably the main factors governing the N2O emission dynamics. Overall, these results highlight the substantial role of NH2OH oxidation and N2O consumption in N2O release in redox-dynamic soils of estuarine intertidal wetlands.

Isotope Depletion Mass Spectrometry (ID-MS) for Accurate Mass Determination and Improved Top-Down Sequence Coverage of Intact Proteins.

Top-down mass spectrometry (MS) is an increasingly important technique for protein characterization. However, in many biological MS experiments, the practicality of applying top-down methodologies is still limited at higher molecular mass. In large part, this is due to the detrimental effect resulting from the partitioning of the mass spectral signal into an increasing number of isotopic peaks as molecular mass increases. Reducing the isotopologue distribution of proteins via depletion of heavy stable isotopes was first reported over 20 years ago (Marshall, A. G.; Senko, M. W.; Li, W.; Li, M.; Dillon, S., Guan, S.; Logan, T. M.. Protein Molecular Mass to 1 Da by 13C, 15N Double-Depletion and FT-ICR Mass Spectrometry. J. Am. Chem. Soc. 1997, 119, 433-434.) and has been demonstrated for several small proteins. Here we extend this approach, introducing a new highly efficient method for the production of recombinant proteins depleted in 13C and 15N and demonstrating its advantages for top-down analysis of larger proteins (up to ∼50 kDa). FT-ICR MS of isotopically depleted proteins reveals dramatically reduced isotope distributions with monoisotopic signal observed up to 50 kDa. In top-down fragmentation experiments, the reduced spectral complexity alleviates fragment-ion signal overlap, the presence of monoisotopic signals allows assignment with higher mass accuracy, and the dramatic increase in signal-to-noise ratio (up to 7-fold) permits vastly reduced acquisition times. These compounding benefits allow the assignment of ∼3-fold more fragment ions than comparable analyses of proteins with natural isotopic abundances. Finally, we demonstrate greatly increased sequence coverage in time-limited top-down experiments-highlighting advantages for top-down LC-MS/MS workflows and top-down proteomics.

Stable carbon isotope analyses offer insights into net carbon degradation of maize silages in anaerobic batch fermentations

Carbon degradation indicates the efficiency of anaerobic digestion processes. Common carbon degradation determination methods define gross carbon degradation (C deggross) of substrate and inoculum inseparably. The aim of this study was to test an isotope-based method defining solely substrate-based net carbon degradation (C degnet) on maize silage. As the natural abundance of stable isotopes in agricultural substrates vary, the method’s applicability was tested on (i) different maize silages sampled from agricultural farms, (ii) maize silage in fresh (MSfresh) and impaired storage (MSimpaired) conditions.Experiments included six maize silages digested in a total of 19 lab-scale batch reactors, analyzed for digestion parameters, stable isotopes, gross and net carbon degradation. MSimpaired showed significantly different stable carbon isotope composition at the start of the experiments, compared to MSfresh. Both methods indicated quality losses in MSimpaired. Results showed significantly higher C degnet values, ranging from 58.4% to 86.5%, compared to deggross values, ranging from 23.1% to 48.7%. This indicated the applicability of an isotope-based method C degnet to assess net carbon degradation of maize silages more detailed by excluding the masking effect of the inoculum. The isotope-based net carbon degradation method was found applicable on maize silages from (i) different farms and (ii) in different storage qualities.

Synthesis and evaluation of thermal neutron attenuation properties of lithium orthosilicate for its application as a beam shaping material on BNCT facilities

Thermal neutron attenuation capacity of Li4SiO4 was evaluated to assess its potential capabilities as a beam shaping material for boron neutron capture therapy (BNCT) facilities. Samples of Li4SiO4 were prepared by two different synthesis methods, using different raw materials and were characterized using x-ray, electron diffraction and transmission electron microscopy. Neutron measurements were performed at the BNCT and the neutron radiography facilities of Centro Atómico Bariloche. Considering its natural isotopic abundance, Li4SiO4 proved to be remarkably effective in comparison with other neutron-absorbing materials. Given the availability of natural Lithium in local salt mines and the scalable feasibility, Li4SiO4 qualifies as a potential material for BNCT beam shaping applications.

Software Supporting a Workflow of Quantitative Dynamic Flux Maps Estimation in Central Metabolism from SIRM Experimental Data.

Stable isotope-resolved metabolomics (SIRM), based on the analysis of biological samples from living cells incubated with artificial isotope enriched substrates, enables mapping the rates of biochemical reactions (metabolic fluxes). We developed software supporting a workflow of analysis of SIRM data obtained with mass spectrometry (MS). The evaluation of fluxes starting from raw MS recordings requires at least three steps of computer support: first, extraction of mass spectra of metabolites of interest, then correction of the spectra for natural isotope abundance, and finally, evaluation of fluxes by simulation of the corrected spectra using a corresponding mathematical model. A kinetic model based on ordinary differential equations (ODEs) for isotopomers of metabolites of the corresponding biochemical network supports the final part of the analysis, which provides a dynamic flux map.

First search for $$\alpha $$ decays of naturally occurring Hf nuclides with emission of $$\gamma $$ quanta

The first ever search for $\alpha$ decays to the first excited state in Yb was performed for six isotopes of hafnium (174, 176, 177, 178, 179, 180) using a high purity Hf-sample of natural isotopic abundance with a mass of 179.8 g. For $^{179}$Hf, also $\alpha$ decay to the ground state of $^{175}$Yb was searched for thanks to the $\beta$-instability of the daughter nuclide $^{175}$Yb. The measurements were conducted using an ultra low-background HPGe-detector system located 225 m underground. After 75 d of data taking no decays were detected but lower bounds for the half-lives of the decays were derived on the level of $\lim T_{1/2}\sim 10^{15}-10^{18}$~a. The decay with the shortest half-life based on theoretical calculation is the decay of $^{174}$Hf to the first $2^+$ 84.3~keV excited level of $^{170}$Yb. The experimental lower bound was found to be $T_{1/2}\geq 3.3\times 10^{15}$ a.

Conformational investigation of peptides using solid-state NMR spectroscopy-A study of polymorphism of β-turn peptides containing diprolines.

The construction of complex protein folds relies on the precise conversion of a linear polypeptide chain into a compact 3-dimensional structure. In this context, study of isolated secondary structural modules containing short stretches of amino acids assumes significance. Additionally, peptides, both natural and synthetic, play a major role as potential drugs. With a view to understand the local conformations adopted by peptides in the solid state, we propose a multinuclear NMR approach utilizing spectra of nuclei in their natural isotopic abundance. Various solid-state NMR experiments have been utilized for assignment of the spectra. Additionally, the gauge-including projector augmented-wave (GIPAW) calculations were used to confirm the assignments. Particularly, the utility of the double-quantum-single-quantum correlation experiments is highlighted for the purpose of assignment and for inferring the conformation across the peptide bond. The methodology is illustrated for the case of designed peptides containing diproline residues occurring at the β-turns for identifying their cis-trans conformational polymorphism. The proposed method promises to be of use in the study of conformations of small- to medium-sized peptides such as antimicrobial peptides and in the study of polymorphism leading to applications in drug development protocols.

Matrix isolation spectroscopy and spectral simulations of isotopically substituted C60 molecules.

Isotopically enriched (3.5% 13C) and depleted (0.5% 13C) fullerene C60 molecules are isolated in parahydrogen (pH2) solids at cryogenic temperatures and studied by high resolution (0.01-0.1 cm-1) infrared (IR) absorption measurements. Spectra of natural isotopic abundance (1.1% 13C) C60 molecules isolated in solid pH2, orthodeuterium (oD2), and Ne matrix hosts serve to identify the relatively minor spectral perturbations due to the trapping environments. Spectral features observed for the four IR-active T1u modes of threefold degeneracy in Ih symmetry, namely, T1u(1) at 529.77 cm-1, T1u(2) at 578.24 cm-1, T1u(3) at 1184.7 cm-1, and T1u(4) at 1432 cm-1, are assigned to the superpositions of matrix perturbed vibrational-mode spectra of a number of 13Cn 12C60-n isotopologues. New molecular orbital calculations show the symmetry lowering effects of 13C substitution, namely, split vibrational frequencies and modified IR intensities. IR spectral patterns calculated for the 328 distinct isotopomers of 13Cn 12C60-n up to n = 3 are used to satisfactorily simulate most of the observed absorption features. For the T1u(4) mode at 1432 cm-1, the observed splitting is insensitive to the 13C abundance, indicating spectral perturbations due to Fermi resonance. Weak absorption features at 1545 cm-1 are assigned to a combination of lower frequency modes. We discuss relative and absolute band strengths for the astrophysical application of estimating C60 abundances in planetary nebulae.

Measurement of the total neutron-scattering cross-section ratios of noble gases of natural isotopic composition using a pulsed neutron beam

Precision measurements of slow neutron cross sections with atoms have several scientific applications. In particular the n-$^{4}$He s-wave scattering length is important to know both for helping to constrain the nuclear three-body interaction and for the proper interpretation of several ongoing slow neutron experiments searching for other types of neutron-atom interactions. We present new measurements of the ratios of the neutron differential scattering cross sections for natural isotopic-abundance mixtures of the noble gases He, Ar, Kr, and Xe to natural isotopic abundance Ne. These measurements were performed using a recently developed neutron scattering apparatus for gas samples located on a pulsed slow neutron beamline which was designed to search for possible exotic neutron-atom interactions and employs both neutron time of flight information and a position-sensitive neutron detector for scattering event reconstruction. We found agreement with the literature values of scattering cross sections inferred from Ar/Ne, Kr/Ne and Xe/Ne differential cross section ratios over the $q$ range of $1 - 7$ nm$^{-1}$. However for the case of He/Ne we find that the cross section inferred differs by 11.3% (7.6 $\sigma$) from previously-reported values inferred from neutron phase shift measurements, but is in reasonable agreement with values from other measurements. The very large discrepancy in the He/Ne ratio calls for a new precision measurement of the n-$^{4}$He scattering length using neutron interferometry.

Biosynthesis of Isoprene Units in Euphorbia lathyris Laticifers vs. Other Tissues: MVA and MEP Pathways, Compartmentation and Putative Endophytic Fungi Contribution.

Euphorbia species are characterized by a net of laticifers producing large amounts of triterpenes. These hydrocarbon-like metabolites can be converted into fuel by the methods of the oil industry. Euphorbia lathyris is easily grown at an industrial scale. In an attempt to increase its triterpene production, the metabolic pathways leading to isoprenoid were investigated by incorporation of 13C labeled glucose and mevalonate and 2H labeled deoxyxylulose as well as by natural abundance isotope ratio GC-MS. Latex triterpenes are exclusively synthesized via the mevalonate (MVA) pathway: this may orient future search for improving the triterpene production in E. lathyris. Phytosterols and their precursors are mainly derived from MVA pathway with a slight contribution of the methylerythritol phosphate (MEP) pathway, whereas phytol is issued from MEP pathway with a minor contribution of the MVA pathway: this is in accordance with the metabolic cross-talk between cytosolic and plastidial compartments in plants. In addition, hopenol B behaved differently from the other latex triterpenes. Its 13C isotope abundance after incorporation of 13C labeled glucose and its natural abundance δ2H signature clearly differed from those of the other latex triterpenes indicating another metabolic origin and suggesting that it may be synthesized by an endophytic fungus.

Isotopic and chemical evidence for nitrate sources and transformation processes in a plateau lake basin in Southwest China

In recent decades, multiple occurrences of algal blooms have substantially deteriorated water quality, especially for the nutrient budget in plateau lakes. Specifically, NO3− pollution has critically threatened groundwater quality, thus increasing human health risk if groundwater serves as a drinking source. To identify the origin and fate of NO3− in a plateau lake basin, we utilized nitrate isotope natural abundance and water chemistry information under land use frameworks and groundwater flow information. In December 2018, we collected water samples from aquifers (n = 33), rivers (n = 2), soil (n = 7), and lakes (n = 4) in Chenghai Lake basin, Southwest China. Our results showed that nearly 41% of groundwater samples failed to meet the drinking water standard of WHO and China (GB/T 5749-2006) of 50 mg/L for NO3− during the dry season. The high variation of δ15N-NO3− (from −3.3 to +41.3‰) and δ18O-NO3− (from −6.4 to +13.6‰) indicated multiple N sources and N cycling processes. Our analysis revealed that 16%–80% of nitrate in groundwater was derived from accumulated soil N, whereas 13%–76% was contributed from manure/landfill leachate. The contribution from atmospheric nitrogen deposition to aquifers was less than 3%. Manure/landfill and soil nitrogen were the primary N sources, contributing for 38.9% and 35.3% to N loading in lake. As for river water, soil nitrogen contributed for 69.7% and 37.2% in R1 and R2, respectively. The denitrification process significantly affects nitrate attenuation of N sources in aquifers. An increasing trend in NO3− concentration was noticed along the groundwater flow path (A-A’) from mountain area to lake. Among different pathways, distinct nitrate sources loading downwards to the aquifers were observed in massive farmlands and residential areas. Thus, the information on both land-use and groundwater flow pathways is indispensable for modelling nitrate sources and transformation processes using the dual isotope approach.

A Gas Chromatography-Molecular Rotational Resonance Spectroscopy Based System of Singular Specificity.

We designed and demonstrated the unique abilities of the first gas chromatography-molecular rotational resonance spectrometer (GC-MRR). While broadly and routinely applicable, its capabilities can exceed those of high-resolution MS and NMR spectroscopy in terms of selectivity, resolution, and compound identification. A series of 24 isotopologues and isotopomers of five organic compounds are separated, identified, and quantified in a single run. Natural isotopic abundances of mixtures of compounds containing chlorine, bromine, and sulfur heteroatoms are easily determined. MRR detection provides the added high specificity for these selective gas-phase separations. GC-MRR is shown to be ideal for compound-specific isotope analysis (CSIA). Different bacterial cultures and groundwater were shown to have contrasting isotopic selectivities for common organic compounds. The ease of such GC-MRR measurements may initiate a new era in biosynthetic/degradation and geochemical isotopic compound studies.

A Gas Chromatography‐Molecular Rotational Resonance Spectroscopy Based System of Singular Specificity

AbstractWe designed and demonstrated the unique abilities of the first gas chromatography–molecular rotational resonance spectrometer (GC‐MRR). While broadly and routinely applicable, its capabilities can exceed those of high‐resolution MS and NMR spectroscopy in terms of selectivity, resolution, and compound identification. A series of 24 isotopologues and isotopomers of five organic compounds are separated, identified, and quantified in a single run. Natural isotopic abundances of mixtures of compounds containing chlorine, bromine, and sulfur heteroatoms are easily determined. MRR detection provides the added high specificity for these selective gas‐phase separations. GC‐MRR is shown to be ideal for compound‐specific isotope analysis (CSIA). Different bacterial cultures and groundwater were shown to have contrasting isotopic selectivities for common organic compounds. The ease of such GC‐MRR measurements may initiate a new era in biosynthetic/degradation and geochemical isotopic compound studies.

Design Parameters of Tissue‐Engineering Scaffolds at the Atomic Scale

AbstractStem‐cell behavior is regulated by the material properties of the surrounding extracellular matrix, which has important implications for the design of tissue‐engineering scaffolds. However, our understanding of the material properties of stem‐cell scaffolds is limited to nanoscopic‐to‐macroscopic length scales. Herein, a solid‐state NMR approach is presented that provides atomic‐scale information on complex stem‐cell substrates at near physiological conditions and at natural isotope abundance. Using self‐assembled peptidic scaffolds designed for nervous‐tissue regeneration, we show at atomic scale how scaffold‐assembly degree, mechanics, and homogeneity correlate with favorable stem cell behavior. Integration of solid‐state NMR data with molecular dynamics simulations reveals a highly ordered fibrillar structure as the most favorable stem‐cell scaffold. This could improve the design of tissue‐engineering scaffolds and other self‐assembled biomaterials.