Influence of pigments and protein aging on protein identification in historically representative casein-based paints using enzyme-linked immunosorbent assay.

A systematic study on the influence of pigments and sample aging on casein identification was performed on 30 reconstructed paints. The protein in all the paints was extracted into solution for analysis. The amount of protein that can be retrieved for solution-based analysis in each of the reconstructed paints was studied with a well-developed NanoOrange method before and after artificial aging.

Solution dependence of the collisional activation of ubiquitin [M + 7H](7+) ions.

The solution dependence of gas-phase unfolding for ubiquitin [M + 7H](7+) ions has been studied by ion mobility spectrometry-mass spectrometry (IMS-MS). Different acidic water:methanol solutions are used to favor the native (N), more helical (A), or unfolded (U) solution states of ubiquitin. Unfolding of gas-phase ubiquitin ions is achieved by collisional heating and newly formed structures are examined by IMS.

Chirality and packing in small proline clusters.

The chiral composition of amino acid clusters may be related to the origin of chirality in biological systems. Here, we use ion mobility/mass spectrometry techniques to investigate the gas phase structures of singly charged proline clusters containing two to six monomers. Using deuterated L-proline (L(D7)) and different electrospray solution compositions varying from enantiopure (50:50 L:L(D7)) to racemic (50:50 L(D7):D), it is possible to study collision cross sections of L-, D-, and mixed xL:xD-proline clusters (where x refers to the number of monomers).

Oscillations of chiral preference in proline clusters.

Ion mobility/mass spectrometry techniques are used to study the chiral preferences of small proline clusters (containing 2 to 23 proline monomers) produced by electrospray ionization. By varying the composition of the electrospray solution from enantiomerically pure (100% L or 100% D) to racemic (50:50 L:D), it is possible to delineate which cluster sizes prefer homochiral (resolved) or heterochiral (antiresolved) compositions. The results show a remarkable oscillation in chiral preference.

Collisional activation of [14Pro+2H]2+ clusters: chiral dependence of evaporation and fission processes.

Ion mobility/mass spectrometry techniques are used to investigate the dissociation of the small proline cluster [14Pro+2H](2+) produced by electrospray ionization. While this cluster is known to prefer heterochiral compositions (i.e.

Transitions between elongated conformations of ubiquitin [M+11H]11+ enhance hydrogen/deuterium exchange.

Hydrogen/deuterium (H/D) exchange reactions between different elongated conformations of [M + 11H](11+) ions of ubiquitin and D(2)O are studied by a combination of ion mobility spectrometry (IMS) and mass spectrometry techniques. Three conformers (B, C, and D), resolved in the IMS separation, each exchange ∼27 hydrogens upon exposure to 0.06 Torr of D(2)O vapor for ∼35 to 40 ms.