cis‐Di­chloro­(di­methyl­aminomethyl­ene)­(tri­phenyl­phosphine)palladium(II) acetone solvate

The synthesis and X‐ray structural analysis of the title compound, [PdCl₂(C₃H₇N)(C₁₈H₁₅P)]·C₃H₆O, are described. The crystal structure contains discrete monomeric mol­ecules of the carbene complex and solvent mol­ecules separated by normal van der Waals distances. The Pd atom is four‐coordinate in an essentially square‐planar environment, with the chlorine ligands mutually cis; Pd—P = 2.2495 (7), Pd—Cl = 2.3508 (7) and 2.3600 (7), Pd—C 1.948 (2) and N—C(carbene) 1.274 (3) Å.     

A hydrogen-bonded adduct containing seven-component supramolecular aggregates

The title compound is a salt, 3,6,9,16,19,22-hexaaza­tri­cyclo­[22.2.2.2^11,14]­triaconta-1(26),11(29),12,14(30),24,27-hexa­ene–3,5-di­nitro­benzoic acid–methanol (1/4/2), C₂₄H₄₂N₆⁴⁺·4C₇H₃N₂O₆⁻·2CH₄O, in which the cation lies across a centre of inversion and one of the two independent anions is positionally disordered over two sets of atom sites having equal occupancy. The components are linked by four types of N—H⃛O hydrogen bond [N⃛O 2.674 (2)–2.815 (2) Å; N—H⃛O 149–163°] and one type of O—H⃛O hydrogen bond in which the acceptor is disordered over two closely adjacent sites [O⃛O 2.67 (4) and 2.75 (4) Å; O—H⃛O 172 and 173°], forming centrosymmetric seven-component aggregates.     

The origins of the colours of yellow,green and blue sapphires

The absorption spectra of natural yellow sapphires are shown to be due to single Fe³⁺ and Fe³⁺  O²⁻  Fe³⁺ pairs, with the latter dominant. Blue and green sapphires have spectra dominated by Fe³⁺  O²⁻  Ti⁴⁺ and Fe²⁺  O²⁻  Fe³⁺ pairs.     

Determination of dissociation temperature for ArO in inductively coupled plasma-mass spectrometry: Effects of excited electronic states and dissociation pathways

The method of comparing experimental and calculated ion ratios to determine a gas kinetic temperature (T_gas) characteristic of the origin of a polyatomic ion in inductively coupled plasma-mass spectrometry (ICP-MS) is applied to ArO⁺. Repeated measurements of ion ratios involving this species yield erratic T_gas values. Complications arise from the predicted presence of a low-lying excited electronic state (²Π) above the ⁴Σ ground state. Omission of this excited state yields unreasonably high temperatures (> 10,000 K) for nine out of nineteen trials. Inclusion of the excited electronic state in the partition function of ArO⁺ causes temperatures to increase further. The problem appears to be related to the prediction that ArO⁺ in the ²Π excited state dissociates into Ar⁺ and O, different products than ArO^{+ 4}Σ which dissociates into Ar and O⁺. Adjustments to the calculations to account for these different products yield reasonable temperatures (2100 to 3500 K) that are consistent from day-to-day and similar to those seen for other weakly-bound polyatomic ions.     

An intraindividual study of the characteristics of erythema induced by bath and oral methoxsalen photochemotherapy and narrowband ultraviolet B

We compared the characteristics of psoralen and ultraviolet A (PUVA) erythema in skin photosensitized by bath or oral methoxsalen in 20 subjects. Erythema was assessed visually and with a reflectance instrument at 24 h intervals for 7 days. In addition, narrowband ultraviolet B (TL-01 UVB) erythema was examined in 19 of these subjects at 4, 8, 12, 24, 48 and 72 h and in another nine subjects at 12, 15, 18, 21 and 24 h. Both bath and oral PUVA exhibited broad erythemal peaks beyond 72 h. For topical PUVA the lowest minimal phototoxic dose (MPD) occurred at 120 and 144 h (P = 0.01 and 0.03 compared with 72 h). Oral PUVA erythema peaked earlier at 96 h: the MPD was significantly lower at 96, 120 and 144 h compared with 72 h (P = 0.001, 0.01 and 0.02, respectively). At 120 h, bath PUVA had a significantly steeper slope compared with oral PUVA. The TL-01 UVB minimal erythema dose was significantly lower at 12 h compared with 24 h (P = 0.019). The majority of subjects were at maximal erythema at 12 h (22 of 28) and 15 h (eight of nine). Our results suggest that peak erythema for bath PUVA, oral PUVA and TL-01 UVB occurs at 120, 96 and 12-15 h, respectively.     

Proteome analyses using accurate mass and elution time peptide tags with capillary LC time-of-flight mass spectrometry

We describe the application of capillary liquid chromatography (LC) time-of-flight (TOF) mass spectrometric instrumentation for the rapid characterization of microbial proteomes. Previously (Lipton et al., Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 11049) the peptides from a series of growth conditions of Deinococcus radiodurans have been characterized using capillary LC MS/MS and accurate mass measurements which are captured as an accurate mass and time (AMT) tag database. Using this AMT tag database, detected peptides can be assigned using measurements obtained on a TOF due to the additional use of elution time data as a constraint. When peptide matches are obtained using AMT tags (i.e., using both constraints) unique matches of a mass spectral peak occurs 88% of the time. Not only are AMT tag matches unique in most cases, the coverage of the proteome is high; approximately 3500 unique peptide AMT tags are found on average per capillary LC run. From the results of the AMT tag database search, approximately 900 ORFs detected using LC-TOFMS, with approximately 500 ORFs covered by at least two AMT tags. These results indicate that AMT database searches with modest mass and elution time criteria can provide proteomic information for approximately one thousand proteins in a single run of <3 h. The advantage of this method over using MS/MS based techniques is the large number of identifications that occur in a single experiment as well as the basis for improved quantitation. For MS/MS experiments, the number of peptide identifications is severely restricted because of the time required to dissociate the peptides individually. These results demonstrate the utility of the AMT tag approach using capillary LC-TOF MS instruments, and also show that AMT tags developed using other instrumentation can be effectively utilized.