Labor pains

We are obtaining and accumulating a lot of data lately which pleases all of us and makes us pretty busy collecting data writing manuscripts. This is a good aspect after learning, practicing, and researching on our one of aggressive projects that is an investigation of structural analysis of glycan structures based on the energy-resolved mass spectrometry for about five years. We developed a series of unique methods including obtaining information regarding “pureness” of a totally unknown analyte. However, bad aspect is that our new results are not accepted by scientific community. We became to believe the problem is that some of our data denies or at least questions what others believe. This is unfortunate but this is the fact we obtained and that no one can deny it. But, this may suggest we are dealing with delicate and important matters. We try ourselves to calm down and to understand this is just a labor pains that will pass in time. And then, bright future waits for us.

Energy-resolved mass spectrometry of oligosaccharide

The structural analysis of glycoproteins is an issue that needs to be addressed in terms of disease diagnosis and individualized healthcare in the future. The rapid analysis of complex carbohydrate molecules obtained from body samples, where the sample amounts are limited, will become important from the perspective of reducing the burden on the patient at the time of an on-site diagnosis.

Methods based on mass spectrometry are expected to be candidates in this regard. However, the three dimensional structure cannot be obtained, thus, the NMR and X-ray crystallography have to be considered. There is a little crystal data of glycoprotein so far. The reason associates to the problem of a glycoform in crystallization. That is of course a problem in NMR as well, but crystallization is not necessary at least. It is considered that availability of labeled molecules becomes the neck. It is long way to overcome the problems in structural glycobiology, such as issues in anomericity, regio isomers, and glycoform.

The diverse research direction intended for an analysis of a single cell to an individual is emerging. A breakthrough-research is expected to match the current diverse research field and for the future glycobiology. The molecular structure is the basis of all phenomena, and thus, discussion regarding functions of glycan makes no sense without it. As a fundamental analytical method and technology, it can be said that “A small thing will serve for a large one.” A method has to be capable of analyzing a small amount of a sample. It might be important interfacing different technologies in diverse fields. Also, convergence of practical and theoretical approaches may be a door to the success.

Technology regarding the qualitative analysis of glycoproteins based on mass spectrometry is now at the level of simultaneous analysis and quasi-top-down analysis, as well of course the traditional analysis of individual molecules. However, the analysis of structural isomers found in oligosaccharides is still a major issue to be addressed. Mass spectrometry essentially cannot distinguish between structural isomers having the same molecular weight. This is true for m/z analysis, but it is well known that MS/MS spectra of ions associated with these isomeric compounds are often different from each other. The phenomenon is now used in structural analysis based on spectral matching. In addition to these qualitative methods, it is considered that more quantitative data analysis is required for establishment of a reliable method. The apparent importance lies in the spectral differences in MS/MS data for structural isomers. The basis of the different heights of a fragment ion observed for the structural isomers is believed to be related to the bond energies of similar but different chemical bonds and/or sites of coordination of metal species etc. Thus, the handling of quantitative data is of extreme importance. Another major issue is that of data compatibility. Without overcoming this problem, methods based on databases will most likely never come to fruition. There have been notable advances in recent research on the structural elucidation of oligosaccharides using mass spectrometry.

Our aim is to contribute to the establishment of structural elucidation method based on mass spectrometry. For this, we believe that the quantitative aspect is one of the most important issues. In order to address the issue, we rely on a method called energy-resolved mass spectrometry (ERMS), which provides energy dependency of fragmentation reactions under collision induced dissociation conditions. We elected the combinatorial library compounds of trisaccharides to analyze the dissociation reactions in detail based on ERMS. A series of compounds is excellent source of structural information. Up until now, we discovered a rule regarding the dissociations of anomers,

References

1. 1.Shioiri, Y. Suzuki, K. Kanie, O. A mechanism of a novel gas-phase reaction via five-membered transition state: Dissociation reaction of 4-aminobutyl glycosides under CID MS/MS conditions. J. Mass Spectrom., 2008, 43, 1132-1139.
   

2. 2.Suzuki, K. Daikoku, S. Ako, T. Shioiri, Y. Kurimoto, A. Ohtake, A. Sarkar, S. K. Kanie, O. High yielding and controlled dissociation of glycosides producing B- and C-ion species under CID MS/MS conditions and use in structure determination. Anal. Chem., 2007, 79, 9022-9029.
   

3. 3.Daikoku, S. Ako, T. Kato, R. Ohtsuka, I. Kanie, O. Discrimination of 16 structural isomers of fucosyl galactose based on energy-resolved mass spectrometry (ERMS). J. Am. Soc. Mass Spectrom., 2007, 18, 1873-1879.
   

4. 4.Kurimoto, A. Kanie, O. Distinguishing isomeric pyridylaminated high-mannose (Man7) oligosaccharides based on energy-resolved mass spectra (ERMS). Rapid Commun. Mass Spectrom., 2007, 21, 2770-2778.
   

5. 5.Daikoku, S. Ako, T. Kurimoto, A. Kanie, O. Anomeric Information obtained from a series of synthetic trisaccharides using energy-resolved mass spectra. J. Mass Spectrom., 2007, 42, 714-723.
   

6. 6.Kurimoto, A. Daikoku, S. Mutsuga, S. Kanie, O. Analysis of energy-resolved mass spectra at MSn in a pursuit to characterize structural isomers of oligosaccharides. Anal. Chem., 2006, 78, 3461-3466.