Unit resolution mass spectra of 112 kDa molecules with 3 Da accuracy

Previously, the highest molecular weight for a sample yielding a unit resolution mass spectrum was 67 kDa (marginal at 86 kDa), obtained with a 6. 2 T Fourier-transform mass spectrometer with electrospray ionization. Now with a 9. 4 T instrument, resolving power of 170,000 has been achieved for chondroitinase I (997 amino acids) and II (990 amino acids), making possible molecular weight assignments of 112,509 and 111,714, respectively, versus 112,508 and 111,713 calculated. Assisting these assignments was the noise reduction in the resolved isotopic peaks achieved by the time domain data sampling technique introduced by Senko, Marshall, and co-workers.     

Infrared photodissociation of non-covalent adducts of electrosprayed nucleotide ions

Efficient dissociation of gaseous non-covalent adducts of multiply charged DNA anions can be effected by infrared irradiation to yield minimal dissociation of the DNA molecular ions-far less dissociation than by collisional activation. Examples include removal of adducted impurities from 100-mer DNA anions and removal of all 14 adducted molecules of 1,4-diaminobutane from M^15? to M^17? of a 50-mer DNA.     

Catalytic Mechanism of Fatty Acid Photodecarboxylase: On the Detection and Stability of the Initial Carbonyloxy Radical Intermediate

In fatty acid photodecarboxylase (FAP), light-induced formation of the primary radical product RCOO⋅ from fatty acid RCOO⁻ occurs in 300 ps, upon which CO₂ is released quasi-immediately. Based on the hypothesis that aliphatic RCOO⋅ (spectroscopically uncharacterized because unstable) absorbs in the red similarly to aromatic carbonyloxy radicals such as 2,6-dichlorobenzoyloxy radical (DCB⋅), much longer-lived linear RCOO⋅ has been suggested recently. We performed quantum chemical reaction pathway and spectral calculations. These calculations are in line with the experimental DCB⋅ decarboxylation dynamics and spectral properties and show that in contrast to DCB⋅, aliphatic RCOO⋅ radicals a) decarboxylate with a very low energetic barrier and on the timescale of a few ps and b) exhibit little red absorption. A time-resolved infrared spectroscopy experiment confirms very rapid, ≪300 ps RCOO⋅ decarboxylation in FAP. We argue that this property is required for the observed high quantum yield of hydrocarbons formation by FAP.     

Complete large-molecule high-resolution mass spectra from 50-femtomole microvolume injection

For electrospray ionization in Fourier-transform mass spectrometry, direct injection of 5×10^?14 mol (0.5 µL of 100 nM from a microvolume sample valve) of ubiquitin (8565 Da) into the flowing solvent stream yields a spectrum with 85:1 signal-to-noise ratio, 2-ppm mass accuracy, and isotopic resolution. Gated trapping for 100 µs from a 0.15-µL/min injection of 20-µM ubiquitin consumes 5×10^?18 mol, which produces a spectrum with 23:1 signal-to-noise ratio and τ;3×10⁵ resolving power.     

High-resolution ion isolation with the ion cyclotron resonance capacitively coupled open cell

For ion cyclotron resonance, a capacitively coupled open cell variant with fourfold radial symmetry was constructed and tested for axial excitation-ejection of large ions at high resolution. With a reverse of frequency sweep direction, this cell gave substantial improvements in signal-to-noise ratio due to linearization of the excitation electric field. Single isotopic peaks of ubiquitin (8.6-kDa) and carbonic anhydrase (29-kDa) molecular ions could be isolated by selective stored waveform inverse Fourier transform excitation, which yielded an order of magnitude higher isolation resolving power than previously achieved at high mass-to-charge ratio values.     

Exact solutions for extended waves in 1d anharmonic lattices

A cyclic chain of n equal classic particles coupled by anharmonic forces has a set of extended vibrational modes, for which exact solutions are given. This requires for the power law of the forces certain conditions to be fulfilled. Each mode is characterized by a wave number and the undulations of the particles depend on the total energy and on a new constant of motion that formally expresses a kind of angular momentum. Exact solutions for n = 7 with a twelfth power potential are discussed.     

Dirichlet type problems in Hermitian Clifford analysis

Solvability conditions for some Dirichlet type boundary value problems in the framework of Hermitian Clifford analysis are established.