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1. Effects of chemical preservation on bulk and amino acid isotope ratios of zooplankton, fish, and squid tissues

   https://doi.org/10.1002/rcm.8408  

   Hetherington, Elizabeth D.; Kurle, Carolyn M.; Ohman, Mark D.; Popp, Brian N. (April 2019, Rapid Communications in Mass Spectrometry)

   RationaleIt is imperative to understand how chemical preservation alters tissue isotopic compositions before using historical samples in ecological studies. Specifically, although compound‐specific isotope analysis of amino acids (CSIA‐AA) is becoming a widely used tool, there is little information on how preservation techniques affect amino acidδ¹⁵N values. MethodsWe evaluated the effects of chemical preservatives on bulk tissueδ¹³C andδ¹⁵N and amino acidδ¹⁵N values, measured by gas chromatography/isotope ratio mass spectrometry (GC/IRMS), of (a) tuna (Thunnus albacares) and squid (Dosidicus gigas) muscle tissues that were fixed in formaldehyde and stored in ethanol for 2 years and (b) two copepod species,Calanus pacificusandEucalanus californicus, which were preserved in formaldehyde for 24–25 years. ResultsTissues in formaldehyde‐ethanol had higher bulkδ¹⁵N values (+1.4,D. gigas; +1.6‰,T. albacares), higherδ¹³C values forD. gigas(+0.5‰), and lowerδ¹³C values forT. albacares(−0.8‰) than frozen samples. The bulkδ¹⁵N values from copepods were not different those from frozen samples, although theδ¹³C values from both species were lower (−1.0‰ forE. californicusand −2.2‰ forC. pacificus) than those from frozen samples. The mean amino acidδ¹⁵N values from chemically preserved tissues were largely within 1‰ of those of frozen tissues, but the phenylalanineδ¹⁵N values were altered to a larger extent (range: 0.5–4.5‰). ConclusionsThe effects of preservation on bulkδ¹³C values were variable, where the direction and magnitude of change varied among taxa. The changes in bulkδ¹⁵N values associated with chemical preservation were mostly minimal, suggesting that storage in formaldehyde or ethanol will not affect the interpretation ofδ¹⁵N values used in ecological studies. The preservation effects on amino acidδ¹⁵N values were also mostly minimal, mirroring bulkδ¹⁵N trends, which is promising for future CSIA‐AA studies of archived specimens. However, there were substantial differences in phenylalanine and valineδ¹⁵N values, which we speculate resulted from interference in the chromatographic resolution of unknown compounds rather than alteration of tissue isotopic composition due to chemical preservation. 

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2. A molecular fluorophore in citric acid/ethylenediamine carbon dots identified and quantified by multinuclear solid‐state nuclear magnetic resonance

   https://doi.org/10.1002/mrc.4985  

   Duan, Pu; Zhi, Bo; Coburn, Luke; Haynes, Christy L.; Schmidt‐Rohr, Klaus (January 2020, Magnetic Resonance in Chemistry)

   Abstract The composition of fluorescent polymer nanoparticles, commonly referred to as carbon dots, synthesized by microwave‐assisted reaction of citric acid and ethylenediamine was investigated by¹³C,¹³C{¹H},¹H─¹³C,¹³C{¹⁴N}, and¹⁵N solid‐state nuclear magnetic resonance (NMR) experiments.¹³C NMR with spectral editing provided no evidence for significant condensed aromatic or diamondoid carbon phases.¹⁵N NMR showed that the nanoparticle matrix has been polymerized by amide and some imide formation. Five small, resolved¹³C NMR peaks, including an unusual ═CH signal at 84 ppm (¹H chemical shift of 5.8 ppm) and ═CN₂at 155 ppm, and two distinctive¹⁵N NMR resonances near 80 and 160 ppm proved the presence of 5‐oxo‐1,2,3,5‐tetrahydroimidazo[1,2‐a]pyridine‐7‐carboxylic acid (IPCA) or its derivatives. This molecular fluorophore with conjugated double bonds, formed by a double cyclization reaction of citric acid and ethylenediamine as first shown by Y. Song, B. Yang, and coworkers in 2015, accounts for the fluorescence of the carbon dots. Cross‐peaks in a¹H─¹³C HETCOR spectrum with brief¹H spin diffusion proved that IPCA is finely dispersed in the polyamide matrix. From quantitative¹³C and¹⁵N NMR spectra, a high concentration (18 ± 2 wt%) of IPCA in the carbon dots was determined. A pronounced gradient in¹³C chemical‐shift perturbations and peak widths, with the broadest lines near the COO group of IPCA, indicated at least partial transformation of the carboxylic acid of IPCA by amide or ester formation. 

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3. Comparison of δ ¹³ C analyses of individual foraminifer ( Orbulina universa ) shells by secondary ion mass spectrometry and gas source mass spectrometry

   https://doi.org/10.1002/rcm.9658  

   Wycech, Jody B.; Kelly, Daniel Clay; Kozdon, Reinhard; Ishida, Akizumi; Kitajima, Kouki; Spero, Howard J.; Valley, John W. (November 2023, Rapid Communications in Mass Spectrometry)

   Abstract RationaleThe use of secondary ion mass spectrometry (SIMS) to perform micrometer‐scalein situcarbon isotope (δ¹³C) analyses of shells of marine microfossils called planktic foraminifers holds promise to explore calcification and ecological processes. The potential of this technique, however, cannot be realized without comparison to traditional whole‐shell δ¹³C values measured by gas source mass spectrometry (GSMS). MethodsPaired SIMS and GSMS δ¹³C values measured from final chamber fragments of the same shell of the planktic foraminiferOrbulina universaare compared. The SIMS–GSMS δ¹³C differences (Δ¹³C_SIMS‐GSMS) were determined via paired analysis of hydrogen peroxide‐cleaned fragments of modern cultured specimens and of fossil specimens from deep‐sea sediments that were either untreated, sonicated, and cleaned with hydrogen peroxide or vacuum roasted. After treatment, fragments were analyzed by a CAMECA IMS 1280 SIMS instrument and either a ThermoScientific MAT‐253 or a Fisons Optima isotope ratio mass spectrometer (GSMS). ResultsPaired analyses of cleaned fragments of cultured specimens (n = 7) yield no SIMS–GSMS δ¹³C difference. However, paired analyses of untreated (n = 18) and cleaned (n = 12) fragments of fossil shells yield average Δ¹³C_SIMS‐GSMSvalues of 0.8‰ and 0.6‰ (±0.2‰, 2 SE), respectively, while vacuum roasting of fossil shell fragments (n = 11) removes the SIMS–GSMS δ¹³C difference. ConclusionsThe noted Δ¹³C_SIMS‐GSMSvalues are most likely due to matrix effects causing sample–standard mismatch for SIMS analyses but may also be a combination of other factors such as SIMS measurement of chemically bound water. The volume of material analyzed via SIMS is ~10⁵times smaller than that analyzed by GSMS; hence, the extent to which these Δ¹³C_SIMS‐GSMSvalues represent differences in analyte or instrument factors remains unclear. 

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4. Calculated and experimental ¹ H and ¹³ C NMR assignments for cannabicitran

   https://doi.org/10.1002/mrc.5224  

   Wood, Jared S.; Gordon, William H.; Morgan, Jeremy B.; Williamson, R. Thomas (October 2021, Magnetic Resonance in Chemistry)

   Abstract Cannabicitran is an important cannabinoid natural product produced byCannabis sativaand is often found at surprisingly high levels (up to ~10%) in “purified” commercial cannabidiol (CBD) extract preparations. Despite the prevalence of this molecule in CBD oil and other cannabinoid‐related products, and the rapidly expanding interest in cannabinoids for treatment of a wide range of physiological conditions, only unassigned¹H NMR data and partial unambiguous¹³C assignments have been published. Herein, we report the complete¹H and¹³C NMR assignments of cannabicitran and comparatively evaluate the performance of several density functional theory (DFT) methods with varying levels of theory for the calculation of NMR chemical shifts. 

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5. Orchestrating rapid long‐distance signaling in plants with Ca ²⁺ , ROS and electrical signals

   https://doi.org/10.1111/tpj.13492  

   Choi, Won‐Gyu; Miller, Gad; Wallace, Ian; Harper, Jeffrey; Mittler, Ron; Gilroy, Simon (March 2017, The Plant Journal)

   Summary Plants show a rapid systemic response to a wide range of environmental stresses, where the signals from the site of stimulus perception are transmitted to distal organs to elicit plant‐wide responses. A wide range of signaling molecules are trafficked through the plant, but a trio of potentially interacting messengers, reactive oxygen species (ROS), Ca²⁺and electrical signaling (‘trio signaling’) appear to form a network supporting rapid signal transmission. The molecular components underlying this rapid communication are beginning to be identified, such as theROSproducingNAPDHoxidaseRBOHD, the ion channel two pore channel 1 (TPC1), and glutamate receptor‐like channelsGLR3.3 andGLR3.6. The plant cell wall presents a plant‐specific route for possible propagation of signals from cell to cell. However, the degree to which the cell wall limits information exchange between cells via transfer of small molecules through an extracellular route, or whether it provides an environment to facilitate transmission of regulators such asROSor H⁺remains to be determined. Similarly, the role of plasmodesmata as both conduits and gatekeepers for the propagation of rapid cell‐to‐cell signaling remains a key open question. Regardless of how signals move from cell to cell, they help prepare distant parts of the plant for impending challenges from specific biotic or abiotic stresses. 

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