Melting proteins confined in nanodroplets with 10.6 μm light provides clues about early steps of denaturation

Abstract

Ubiquitin confined within nanodroplets was irradiated with a variable-power CO2 laser. Mass spectrometry analysis shows evidence for a protein "melting"-like transition within droplets prior to solvent evaporation and ion formation. Ion mobility spectrometry reveals that structures associated with early steps of denaturation are trapped because of short droplet lifetimes.

A microdroplet-accelerated Biginelli reaction: mechanisms and separation of isomers using IMS-MS

“…Temperature and solvent studies were carried out using variable-temperature nano-ESI source, described in detail previously. 42,66 Many other electrospray parameters had to be optimized including concentration, size of the emitter tip, distance between the ESI emitter and the inlet of the mass spectrometer, and the applied voltage (see ESI † for details). Control NMR experiments were run to ensure that the condensation was not taking place in bulk-phase.…”

“…Recently, the groups of Cooks, [17][18][19][20][21][22][23][24][25][26] Zare, [27][28][29][30][31][32][33][34][35][36][37][38][39] and others [40][41][42][43][44][45][46] have reported the acceleration of reactions in microdroplet environments during the process of electrospraying reagents into a mass spectrometer. 32 Intrigued by the possibility of faster rates for multicomponent reactions, we explored the use of microdroplets as a means of enabling a rapid Biginelli reaction (Scheme 2).…”

Substance P in the Gas Phase: Conformational Changes and Dissociations Induced by Collisional Activation in a Drift Tube

“…In order to maintain proteostasis, denatured structures must be recognized as such, [12] tagged, [13] and destroyed, [14] in order to prevent deleterious consequences such as aggregation. [15][16][17] We have previously quoted [18,19] Lumry's and Eyring's now classic 1954 paper, [20] "Conformation Changes of Proteins" which begins by stating, "[t]he term protein denaturation even in its original meaning included all those reactions destroying the solubility of native proteins and has since acquired so many other meanings as to become virtually useless." In the 65 years since, little has changed.…”

“…[29] Moreover, the evaporative cooling process associated with creating macromolecular ions by electrospray ionization (ESI) [30] rapidly freezes-out specific structures as they dry. [18,31,32] These "freeze-dried biomolecules," as Beauchamp's group called them [33] are now more than a curiosity; they provide access to non-native states where few options exist. And, studies of naked proteins provide the chance to examine intramolecular interactions without complications due to solvent.…”

Time-resolved universal temperature measurements using NaYF4:Er3+,Yb3+ upconverting nanoparticles in an electrospray jet

“…There is need and interest to non-invasively image and measure temperatures in complex systems such as in vivo imaging, cellular biological systems and matrices, whole-blood samples, and electrospray jets used in mass spectrometry [ 1 ]. Optical thermometers using UCNPs are well suited for these applications because near-IR excitation of the UCNPs minimizes tissue damage [ 2 ], is relatively free of background fluorescence [ 3 ], and has a high penetration depth [ 3 – 4 ].…”