We present the construction and performance of a 20-μL active volume probe that utilizes zerosusceptibility wire for the detection transceiver coil and a 3.5 mm outer diameter thin-wall bubble flow cell to contain the sample. The probe shows good rf homogeneity, resolution, line shape and sensitivity. The sensitivity and resolution of the 20-μL probe was compared to those for several other coil configurations, including smaller detection volumes, a thin wire copper coil immersed in susceptibility matching perfluorocarbon FC-43 (fluorinert) fluid, and a standard 5 mm probe. In particular, the 1 H mass sensitivity, S m (SNR per micromole), was 3-4 fold higher than that for the standard 5 mm probe. Finally, the use of the zero-susceptibility wire in smaller volume probes is discussed along with potential future improvements and applications.
Improved NMR detection of mass limited samples can be obtained by taking advantage of the mass sensitivity of microcoil NMR, while throughput issues can be addressed using multiple, parallel sample detection coils. We present the design and construction of a double resonance 300-MHz dual volume microcoil NMR probe with thermally-etched 440-nL detection volumes and fused silica transfer lines for high-throughput stopped-flow or flow-through sample analysis. Two orthogonal solenoidal detection coils and the novel use of shielded inductors allowed the construction of a probe with negligible radio-frequency cross talk. The probe was resonated at 1 H-2 D (upper coil) and 1 H-13 C (lower coil) frequencies such that it could perform 1D and 2D experiments with active locking frequency. The coils exhibited line widths of 0.8 to 1.1 Hz with good mass sensitivity for both 1 H and 13 C NMR detection. 13 C directly detected 2D HETCOR spectra of 5% v/v 13 C labeled acetic acid were obtained in less than 5 min. Demonstration of the probe characteristics as well as applications of the versatile two-coil double resonance probe are discussed.
Recent advances in microcoil NMR have provided commercially available, robust methodologies for analyzing mass and volume limited samples in the low microliter regime, and the technology has been applied in a number of areas. Unfortunately, due to constraints on sample size and the limited solubility of some compounds of interest, the application of this approach to certain areas of development, such as the structural analysis of chromatography eluates, is restricted. A current challenge is to provide an option within a previously unexplored sample size regime (tens of microliters) while still taking advantage of the increase in mass sensitivity afforded by solenoidal microcoil NMR. In this article, we present the design and construction of a microcoil NMR probe with a custom detection cell for the routine analysis of 20-lL samples. The detection cell is comprised of a CO 2 -laser-heated HF-etched borosilicate active volume with fused silica transfer lines added to provide sample input and output. This setup produces an enlarged sample bubble within the detection coil and provides easy connection with 1/16 in. standard LC connections, lending itself to applications with HPLC-NMR, online SPE and similar separation techniques, as well as higher-throughput robotic automation. NMR performance characteristics determined using standard compounds showed the probe exhibited reasonable resolution (<0.01 ppm), although sensitivity was less than optimal due to tuning constraints. Future improvements and opportunities are also discussed.
Nucleosides are indicators of the whole-body turnover of transfer RNA. Based on the activity of cancer cells these molecules could potentially be used as cancer biomarkers, and several studies have determined that the metabolic levels of nucleosides are significantly altered in cancer patients compared to control groups. Here we report a targeted metabolite investigation of serum nucleosides in esophageal adenocarcinoma specimens. We quantified eight nucleosides using high-performance liquid chromatography/triple quadrupole mass spectrometry (HPLC/TQMS) and determined that the metabolic levels of 1-methyladenosine (p <2.14 × 10(-7)), N(2),N(2)-dimethylguanosine (p <2.78 × 10(-7)), N(2)-methylguanosine (p <2.48 × 10(-6)) and cytidine (p <6.98 × 10(-4)) were significantly elevated while the concentration of uridine (p <3.74 × 10(-3)) was significantly lowered in serum samples from cancer patients compared to those of control group. Our results suggest that nucleosides could potentially serve as useful biomarkers to identify esophageal adenocarcinoma.
For mass limited samples, the residual sample volume outside the detection coil is an important concern, as is good base line resolution. Here, we present the construction and evaluation of magnetic susceptibility-matched plugs for microcoil NMR sample cells which address these issues. Mixedepoxy glue and ultem tube plugs that have susceptibility values close to those of perfluorocarbon FC-43 (fluorinert) and copper were used in small volume (0.5 to 2 μL) and larger volume (15 to 20 μL) thin glass capillary sample cells. Using these plugs, the sample volume efficiency (i.e. ratio of active volume to total sample volume in the microcoil NMR cell) was improved by 6 to 12 fold without sensitivity and resolution trade-offs. Comparison with laser etched or heat etched microcoil sample cells is provided. The approaches described are potentially useful in metabolomics for biomarkers detection in mass limited biological samples.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.