Publications by authors named "A Arslanian"
Article Synopsis
- Native mass spectrometry characterizes biomolecular features, but ionization tuning can distort the protein complex's structure, affecting experimental results.
- Surface-induced dissociation (SID) helps determine the native-like topology of protein complexes by causing them to dissociate at their weakest interfaces, but precedes changes in the quaternary structure can alter SID results.
- Electron-capture dissociation (ECD) complements SID by confirming rearranged subunit interfaces after in-source activation, emphasizing the importance of using standard protein complexes when calibrating instruments for accurate native mass spectrometry.
We determined collision cross section (CCS) values for singly and doubly charged cucurbit[]uril ( = 5-7), decamethylcucurbit[5]uril, and cyclohexanocucurbit[5]uril complexes of alkali metal cations (Li-Cs). These hosts are relatively rigid. CCS values calculated using the projection approximation (PA) for computationally modeled structures of a given host are nearly identical for +1 and +2 complexes, with weak metal ion dependence, whereas trajectory method (TM) calculations of CCS for the same structures consistently yield values 7-10% larger for the +2 complexes than for the corresponding +1 complexes and little metal ion dependence.
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- SORI-CRAFTI is a mass spectrometry technique that activates precursor ions to measure their ion-neutral collision cross sections simultaneously with product ions.
- The method was benchmarked using protonated leucine-enkephalin, showing strong agreement (within 1-2%) with earlier results from collision-induced dissociation-ion mobility studies.
- SORI-CRAFTI demonstrated qualitative effectiveness in analyzing alkali metal-cationized leucine-enkephalin and cryptand+Cs, making it a valuable tool for exploring gas-phase ion chemistry in small to medium molecules.
We have employed mass spectrometry, ion mobility, and computational techniques to characterize complexes of -alkylammonium ions with cucurbit[5]uril (CB[5]) and cucurbit[6]uril (CB[6]) ligands in the gas phase. Nonrotaxane structures are energetically preferred and experimentally observed for all CB[5] complexes. Pseudorotaxane structures are computationally favored and experimentally observed for [CB[6]·-alkylammonium] complexes, but the addition of a second cation (proton, alkali metal ion, another alkylammonium ion, or guanidinium) on the opposite rim of CB[6] causes sufficiently unfavorable steric interactions that -pentylammonium and longer chains no longer remain threaded through the CB[6] cavity; nonrotaxane topologies are then favored.
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- The CRAFTI technique for measuring collision cross sections (CCS) faces challenges due to the need for accurate pressure measurements in the mass spectrometer and the requirement that ions must be similar in mass to the neutral particles.
- The newly developed "multi-CRAFTI" method allows researchers to excite multiple ions simultaneously, enabling relative measurements of CCS without needing to know the exact pressure and facilitating absolute CCS measurements using internal standards.
- Experimental results show that multi-CRAFTI produces CCS values in agreement with traditional methods, although it tends to yield smaller CCS due to higher collision energies; the study indicates that computational models may overestimate interactions among the ions, particularly at higher masses.