Trends in co-fractionation mass spectrometry: A new gold-standard in global protein interaction network discovery

Co-fractionation mass spectrometry (CF-MS) uses biochemical fractionation to isolate and characterize macromolecular complexes from cellular lysates without the need for affinity tagging or capture. In recent years, this has emerged as a powerful technique for elucidating global protein-protein interaction networks in a wide variety of biospecimens. This review highlights the latest advancements in CF-MS experimental workflows including machine learning-guided analyses, for uncovering dynamic and high-resolution protein interaction landscapes with enhanced sensitivity, accuracy and throughput, enabling better biophysical characterization of endogenous protein complexes. By addressing challenges and emergent opportunities in the field, this review underscores the transformative potential of CF-MS in advancing our understanding of functional protein interaction networks in health and disease.

Rapid in situ identification of honey authenticity based on RP-Nano-ESI-MS using online desalting

High-content sugar in honey frequently results in severe matrix effects and requires complex pretreatment prior to analysis, posing significant challenges for the rapid analysis of honey. In this study, the reversal polarity nano-electrospray ionization mass spectrometry (RP-Nano-ESI-MS) analysis was developed for the direct evaluation of honey samples. The results indicated that RP-Nano-ESI-MS significantly mitigated the matrix effects induced by high-content sugar through the implementation of online desalting. Furthermore, RP-Nano-ESI-MS has been proven capable of not only differentiating acacia honey adulterated with 10% rape honey, but also effectively distinguishing six types of honey and exhibiting remarkable proficiency in detecting honey adulteration and botanical traceability. Additionally, RP-Nano-ESI-MS exhibited strong quantitative abilities, effectively characterizing variations in amino acid composition among six types of honey with high stability and reproducibility. Our studies underscore the significant potential of RP-Nano-ESI-MS for its rapid in situ analysis of sugar-rich foods like honey, especially in their authenticity verification.

Plastic probe electrospray ionization mass spectrometry developed for rapid fingerprint profile of biological samples without pretreatment

A triangular-shaped flat plastic substrate probe was prepared for direct electrospray ionization mass spectrometry (ESI-MS) for analysis of untreated chemical and biological samples including liquids (Met-Arg-Phe-Ala peptide, reserpine, and dodecyl aldehyde), solids (biological samples, traditional Chinese medicine), and powders (roasted coffee, rhizoma coptidis, lotus plumule, and Schisandra sphenanthera). Quantitative analysis of reserpine in water yielded a detection limit of 1 ng mL-1, dynamic response range within 1-500 ng mL-1, and linearity of signal response ˃0.9925. Compared to the conventional capillary ESI, this plastic probe ESI offers lower cost of analysis (US $0.0056 per probe), higher sensitivity, lower sample consumption, longer signal duration (>6 min), better reproducibility, signal stability, and higher speed of analysis (<10 s per sample, including sample loading). Overall, the results indicate the potential of ESI-MS based on flat plastic probes as a versatile method for simple, sensitive, and stable analysis of untreated biological sample analysis.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2019-2020

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2020. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. The review is basically divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of arrays. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other areas such as medicine, industrial processes and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. The reported work shows increasing use of incorporation of new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented nearly 40 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show little sign of diminishing.

Heat-Assisted Dual Neutral Spray Ionization for High-Performance Online Desalting in Mass Spectrometric Analysis

In mass spectrometry (MS), nonvolatile salts contaminate the transmission system and cause ion suppression, hampering MS analysis. When MS is combined with liquid chromatography (LC) that uses a salty mobile phase, the problems become more intractable due to long analysis time. Here, a novel heat-assisted dual neutral spray ionization (HADSI) method was developed, which projected sample solution spray and solvent spray onto a heated plate to achieve online desalting and high ionization. The experimental parameters of HADSI were optimized, which indicated that the plate temperature was crucial for ionization and desalination. Eight drug compounds dissolved in various commonly used buffers were directly analyzed using HADSI-MS, even though the concentration of PBS buffer reached 500 mmol/L. The established method showed considerable sensitivity in the positive ion mode with the limits of detection at the level of nmol/L, and good linearity (R² > 0.99) was achieved for all the analyzed compounds. The repeatability and intra- and interday precisions of the method were evaluated, demonstrating the feasibility and reliability of the analysis of salty samples by HADSI-MS. Further, the method was demonstrated to tolerate the long-time analysis of high-salt LC eluates and the device was easy to maintain. Finally, a crude roxithromycin product was separated by LC and then analyzed by HADSI-MS, and seven unknown impurities and nine known impurities were successfully detected. Our results indicated that HADSI-MS may have potential applications in academic and industrial fields.

Rapid and flexible online desalting using Nafion-coated melamine sponge for mass spectrometry analysis

RATIONALE

The performance of mass spectrometry (MS) analysis is often affected by the presence of salt ions. To achieve optimal MS detection results, desalting is necessary for samples with high salt concentrations. We report a rapid, low-cost and flexible online desalting method using Nafion-coated sponge. This method is easy to perform and can be implemented to a wide range of customized fluidic systems.

METHODS

Nafion-coated melamine sponge was fabricated by soaking a glass tube containing a melamine sponge in Nafion solution and then drying overnight. The online desalting workflow is comprised of three major parts: (1) Syringe pump, which provides a continuous flow for the online fluid system; (2) Nafion sponge in a glass tube, where the online desalting of sample solution happens; (3) Capillary Vibrating Sharp-Edge Spray Ionization (cVSSI), which is an ionization technique to ionize the desalted analytes.

RESULTS

Effective online desalting of a 10 mM NaCl solution was demonstrated for a wide range of molecules including small molecules, peptides, DNAs, and proteins using a flow rate of 10 μL/min. By incorporating multiple pieces of the Nafion-coated sponge, effective desalting for ubiquitin and cytochrome c (Cyt-c) from physiological buffers, including phosphate-buffered saline (PBS) and tris-buffered saline (TBS), were also achieved. For molecules that are sensitive to low pH conditions after desalting, a R-SO3 NH4 -type Nafion-coated sponge was fabricated. Desalting of ubiquitin, oligosaccharide, and DNA oligomers from 10 mM NaCl or 10 mM KCl solutions was demonstrated.

CONCLUSIONS

Flexible, low-cost, and efficient online desalting was achieved by the Nafion-coated sponge. A variety of molecules ranging from small molecules, peptides, proteins to oligosaccharides and DNAs can be desalted for MS analysis. The desalting by Nafion sponge has great potential for desalting applications that require customized fluidic design and rapid analysis.

A convenient online desalination tube coupled with mass spectrometry for the direct detection of iodinated contrast media in untreated human spent hemodialysates

Background

Mass spectrometry (MS) analysis using direct infusion of biological fluids is often problematic due to high salts/buffers. Iodinated contrast media (ICM) are frequently used for diagnostic imaging purposes, sometimes inducing acute kidney injury (AKI) in patients with reduced kidney function. Therefore, detection of ICM in spent hemodialysates is important for AKI patients who require urgent continuous hemodiafiltration (CHDF) because it allows noninvasive assessment of the patient’s treatment. In this study, we used a novel desalination tube before MS to inject the sample directly and detect ICM.

Methods

Firstly, spent hemodialysates of one patient were injected directly into the electrospray ionization (ESI) source equipped with a quadrupole time-of-flight mass spectrometer (Q-TOF MS) coupled to an online desalination tube for the detection of ICM and other metabolites. Thereafter, spent hemodialysates of two patients were injected directly into the ESI source equipped with a triple quadrupole mass spectrometer (TQ-MS) connected to that online desalination tube to confirm the detection of ICM.

Results

We detected iohexol (an ICM) from untreated spent hemodialysates of the patient-administered iohexol for computed tomography using Q-TOF MS. Using MRM profile analysis, we have confirmed the detection of ICM in the untreated spent hemodialysates of the patients administered for coronary angiography before starting CHDF. Using the desalination tube, we observed approximately 178 times higher signal intensity and 8 times improved signal-to-noise ratio for ioversol (an ICM) compared to data obtained without the desalination tube. This system was capable of tracking the changes of ioversol in spent hemodialysates of AKI patients by measuring spent hemodialysates.

Conclusion

The online desalination tube coupled with MS showed the capability of detecting iohexol and ioversol in spent hemodialysates without additional sample preparation or chromatographic separation. This approach also demonstrated the capacity to monitor the ioversol changes in patients’ spent hemodialysates.

Online discovery of the molecular mechanism for directionally detoxification of Fuzi using real-time extractive electrospray ionization mass spectrometry

ETHNOPHARMACOLOGICAL RELEVANCE

Aconitum carmichaelii Debeaux, a famous traditional medicinal herb for collapse, rheumatic fever, and painful joints, always raises global concerns about its fatal toxicity from toxic alkaloids when improperly processed. Therefore, it is urgent to clarify the internal molecular mechanism of processing detoxification on Aconitum and develop simple and reliable approaches for clinical application, which is also of great significance to the rational medicinal use of Aconitum.

AIM OF THE STUDY

The study aimed at developing a complete molecular mechanism exploration strategy in complex medicinal herb decocting system, clarifying the internal molecular mechanism of processing detoxification on Aconitum, and exploring valid approaches for detoxification.

MATERIALS AND METHODS

Aconiti Lateralis Radix Praeparata (Fuzi) was selected as the model for exploring the complex Aconitum detoxification mechanism using an advanced online real-time platform based on extractive electrospray ionization mass spectrometry. The methods realized the sensitive capture of dynamic trace intermediates, accurate qualitative and quantitative analysis, and real-time and long-term monitoring of multi-components with satisfactory accuracy and resistance to complex matrices.

RESULTS

Components in the complex Aconitum decocting system were real-timely characterized and fat meat was discovered and verified to directionally detoxify Aconitum while reserving the therapy effect. More importantly, the dynamic detoxification mechanism in the chemically complex Aconitum decoction was molecularly profiled. A novel reaction pathway based on nucleophilic substitution reaction mechanism was proposed. As confirmed by the theoretic calculations at DFT B3LYP/6-31G (d) levels, fatty acids (e.g., palmitic acid) acted as a green, cheap, and high-performance catalyst and promote the decomposition of toxic diester alkaloids to non-toxic and active benzoyl-monoester alkaloids through the discovered mechanism.

CONCLUSION

The study exposed a novel detoxification molecular mechanism of Aconitum and provided an effective method for the safe use of Aconitum, which could effectively guide the development of traditional processing technology and compatibility regulation of the toxic herb and had great value to the modernization and standardization development of traditional medicine.

Point Analysis of Foods by Sheath-Flow Probe Electrospray Ionization/Mass Spectrometry (sfPESI/MS) Coupled with a Touch Sensor

For quick, noninvasive, and high-sensitivity surface analysis of foods and agricultural products, a touch sensor was developed and applied to sheath-flow probe electrospray ionization/mass spectrometry (sfPESI/MS). Upon making contact with the sample, the probe stopped by detecting the current flowing through the circuit and analytes on the sample surface were extracted in the solvent preloaded in the plastic capillary. By lifting up the probe to the default position, an electrospray ionization mass spectrum of the sample was obtained. By scanning the sample stage using a programming tool, a point analysis of targeted positions of biological samples with a spot diameter of ≤0.3 mm was achieved. It took less than 10 s for one sample spot. This method was applied to various plants and animal tissues.