Selective Quantitation of Organic Sulfur with the Precursor Scan Method of Neutralization-Reionization Mass Spectrometry

No, Myoung-han; Tureček, František

doi:10.1002/(sici)1096-9888(199708)32:8<838::aid-jms541>3.0.co;2-l

Cited by 3 publications

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“…In particular, the abundant low-mass ions in the þ NR þ mass spectrum of 1 þ , for example, SH þ (m/z 33) and S þ (m/z 32), are often present as secondary fragments of sulfurcontaining ions and arise by convergent dissociations induced by high-energy collisions. 43 Note that most of the dissociation products present in the S3a), which in turn was similar to the standard 70 eV electronÀ ionization mass spectrum of 2 (Figure S3b). Acetenethiolimine (CH 3 C(SH)dNH, 5) 44 from loss of the N-methyl group from 1 is an unstable tautomer of thioacetamide (6) in both the neutral form (ΔH 0 (5 f 6) = À32 kJ mol À1 ) and as cation radicals 1).…”

Section: ' Results and Discussionsupporting

confidence: 63%

“…Postreionization dissociations of 1 and its primary fragments 2 and 5 can also account for the formation of low-mass fragment ions. In particular, the abundant low-mass ions in the + NR + mass spectrum of 1 + , for example, SH + ( m / z 33) and S + ( m / z 32), are often present as secondary fragments of sulfur-containing ions and arise by convergent dissociations induced by high-energy collisions . Note that most of the dissociation products present in the + NR + mass spectrum of 1 + also appeared in the + NR + mass spectrum of 2 +• (Figure S3a), which in turn was similar to the standard 70 eV electron–ionization mass spectrum of 2 (Figure S3b).…”

Section: Resultsmentioning

confidence: 57%

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A Stable Aminothioketyl Radical in the Gas Phase

2011

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We report the first preparation of a stable aminothioketyl radical, CH(3)C(•)(SH)NHCH(3) (1), by fast electron transfer to protonated thioacetamide in the gas phase. The radical was characterized by neutralization-reionization mass spectrometry and ab initio calculations at high levels of theory. The unimolecular dissociations of 1 were elucidated with deuterium-labeled radicals CH(3)C(•)(SD)NHCH(3) (1a), CH(3)C(•)(SH)NDCH(3) (1b), CH(3)C(•)(SH)NHCD(3) (1c), and CD(3)C(•)(SH)NHCH(3) (1d). The main dissociations of 1 were a highly specific loss of the thiol H atom and a specific loss of the N-methyl group, which were competitive on the potential energy surface of the ground electronic state of the radical. RRKM calculations on the CCSD(T)/aug-cc-pVTZ potential energy surface indicated that the cleavage of the S-H bond in 1 dominated at low internal energies, E(int)< 232 kJ mol(-1). The cleavage of the N-CH(3) bond was calculated to prevail at higher internal energies. Loss of the thiol hydrogen atom can be further enhanced by dissociations originating from the B excited state of 1 when accessed by vertical electron transfer. Hydrogen atom addition to the thioamide sulfur atom is calculated to have an extremely low activation energy that may enable the thioamide group to function as a hydrogen atom trap in peptide radicals. The electronic properties and reactivity of the simple aminothioketyl radical reported here may be extrapolated and applied to elucidate the chemistry of thioxopeptide radicals and cation radicals of interest to protein structure studies.

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Section: ' Results and Discussionsupporting

confidence: 63%

Section: Resultsmentioning

confidence: 57%

A Stable Aminothioketyl Radical in the Gas Phase

2011

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Hydrocarbon Processing

Feng

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Flores

2012

Mass Spectrometry Handbook

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E-learning addresses the challenges process companies will face in the near future. It will change working and learning and dramatically improve equipment reliability throughout the process industries. Several technical, financial and cultural commitments are required to successfully implement e-learning."In times of change, it is learners who will inherit the organization. And those who refuse to learn will find themselves well-equipped for an organization that no longer exists." (Kenneth T. Derr, Chairman and CEO, Chevron) The process industries will migrate to daily Internet use to rapidly build the knowledge and expertise of personnel and to greatly expand communication of data and information. The Internet will provide companies the tools required to build true "learning organizations." While process companies are confronted with increasing economic and regulatory demands, the Internet offers incredible opportunities. To remain profitable, process companies must operate their facilities in a manner that is continuously reliable, safe and environmentally responsible. This requires experienced and knowledgeable personnel who have access to information and an organization that is receptive to and capable of change. Meanwhile, a generation of experienced workers is nearing retirement and younger workers are more difficult than ever to attract and retain. This loss of experience threatens to deplete companies of the skills required to compete and remain successful.

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