Novel alkali earth borohydride Sr(BH4)2 and borohydride-chloride Sr(BH4)Cl.

Two novel alkali earth borohydrides, Sr(BH4)2 and Sr(BH4)Cl, have been synthesized and investigated by in-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and Raman spectroscopy. Strontium borohydride, Sr(BH4)2, was synthesized via a metathesis reaction between LiBH4 and SrCl2 by two complementary methods, i.e., solvent-mediated and mechanochemical synthesis, while Sr(BH4)Cl was obtained from mechanochemical synthesis, i.e., ball milling. Sr(BH4)2 crystallizes in the orthorhombic crystal system, a = 6.97833(9) Å, b = 8.39651(11) Å, and c = 7.55931(10) Å (V = 442.927(10) Å(3)) at RT with space group symmetry Pbcn. The compound crystallizes in α-PbO2 structure type and is built from half-occupied brucite-like layers of slightly distorted [Sr(BH4)6] octahedra stacked in the a-axis direction. Strontium borohydride chloride, Sr(BH4)Cl, is a stoichiometric, ordered compound, which also crystallizes in the orthorhombic crystal system, a = 10.8873(8) Å, b = 4.6035(3) Å, and c = 7.4398(6) Å (V = 372.91(3) Å(3)) at RT, with space group symmetry Pnma and structure type Sr(OH)2. Sr(BH4)Cl dissociates into Sr(BH4)2 and SrCl2 at ~170 °C, while Sr(BH4)2 is found to decompose in multiple steps between 270 and 465 °C with formation of several decomposition products, e.g., SrB6. Furthermore, partly characterized new compounds are also reported here, e.g., a solvate of Sr(BH4)2 and two Li-Sr-BH4 compounds.

High-field superconductivity in C-doped MgB2 bulk samples prepared by a rapid synthesis route.

The upper critical field sets the thermodynamic limit to superconductivity. A big gap is present between the upper-critical-field values measured in MgB2 polycrystalline bulk superconductors and those of thin films, where values as high as ~ 50 T have been achieved at 4.2 K. Filling this gap would unlock the potential of MgB2 for magnet applications. This work presents the results of an extensive experimental campaign on MgB2 bulk samples, which has been guided by a Design of Experiment. We modeled the dependence of the upper critical field on the main synthesis parameters and established a new record (~ 35 T at 4.2 K) preparing C-doped bulk samples by a non-conventional rapid-synthesis route. This value appears to be an upper boundary for the upper critical field in bulk samples. Structural disorder in films seems to act selectively on one of the two bands where superconductivity in MgB2 takes place: this enhances the upper critical field while reducing the critical temperature only by few Kelvins. On the other hand, the critical temperature in bulk samples decreases monotonically when structural disorder increases, and this imposes a limit to the maximum achievable upper critical field.

Residual vestibular function after vestibular schwannoma surgery.

OBJECTIVES: This study aimed to assess vestibular function in 39 patients who underwent neurectomy for vestibular schwannoma. METHOD: Semicircular canal reactivity was measured by video head-impulse test using high-frequency passive head acceleration. Response gain was calculated as a ratio between the areas under the eye-velocity curve and the head-velocity curve. STATISTICAL ANALYSIS: Student t-test was used for to compare quantitative variables. ANOVA was used to test inter-group differences in categoric variables. RESULTS: In all cases, surgery-side gain on head impulse test was low, with increased gain asymmetry. A subgroup of 7 patients (18%) showed relatively high gain in vestibulo-ocular reflex on the surgery side. Caloric reaction was absent in all cases. These findings indicate that residual vestibular function can be conserved following vestibular schwannoma extirpation. CONCLUSION: Cases with moderate vestibulo-ocular reflex gain were a subgroup with partial conservation of vestibular nerve fibers. Whether this is a predictor of better functional prognosis remains to be elucidated. Higher gain correlated with less extensive surgery and sparing of the inferior vestibular nerve. Low gain correlated with complete vestibular neurectomy. This information may guide rehabilitation strategy following surgery.

Etiology of acute gastroenteritis in three sentinel general practices, Austria 2007.

BACKGROUND: We studied the etiology of acute gastroenteritis in a village with a total population of approximately 6,000. This is the first study in Austria that has investigated a broad range of pathogens recovered from an unselected population of patients who had consulted general practitioners because of gastroenteritis. MATERIALS AND METHODS: In 2007, all patients who visited one of three local general practitioners for acute gastroenteritis were invited to provide stool specimens to be tested for Salmonella, Shigella, Campylobacter, enterohemorrhagic Escherichia coli (EHEC) (mTSB enrichment [R-Biopharm] followed by toxin ELISA plus culture), enteropathogenic E. coli (EPEC), Yersinia, Vibrio cholerae, Clostridium difficile (toxin plus culture), rotavirus plus adenovirus (RIDA) Quick Rotavirus/Adenovirus Combi test), Giardia duodenalis plus Cryptosporidium parvum (RIDA) Quick Cryptosporidium/Giardia Combi test), astrovirus (ELISA), and norovirus (reverse-transcriptase PCR). RESULTS: Stool specimens were provided by 306 patients (161 female) with acute diarrhea. The ages of the patients ranged from 1 to 89 years (mean 37, median 36). Pathogens were detected in 71 (23.2%) patients, with incidence peaks in February and June. Norovirus accounted for 36.0% of positive results, C. difficile for 18.7%, rotavirus for 17.3%, Campylobacter for 9.3%, Salmonella for 6.6%, adenovirus for 5.4%, G. duodenalis and C. parvum for 2.7% each, and Yersinia enterocolitica for 1.3%. No cases of shigellosis or infection with EHEC, EPEC, or astrovirus were diagnosed. Viruses accounted for 58.7% of the 75 positive results, bacteria for 36.0%, and parasites for 5.3%. CONCLUSION: Our study underlines a dominant role of norovirus and toxigenic C. difficile as etiologic agents of acute gastroenteritis among the patients of general practitioners.

Two cases of improvement of smooth pursuit eye movements after selective posterior rhizotomy.

OBJECTIVE: Selective posterior rhizotomy (SPR) represents a standard neurosurgical approach in the treatment of spasticity in children with cerebral palsy (CP). Beside the reduction of spasticity in lower limbs, SPR may have suprasegmental effects, considerably above the surgery site. In this communication, we report on the improvement of smooth pursuit eye movements (SPEM) in two children after SPR. MATERIAL AND METHODS: Four children with CP underwent SPR. Eye movements were registered by infrared video-oculography before and after the surgery. RESULTS: The analysis of SPEM showed the improvement of the correlation coefficient of the eye response to the stimulus after SPR in two subjects. Improvement of SPEM performance was largely due to suppression of spontaneous fixation nystagmus. CONCLUSION: SPR may lead to the improvement of SPEM in children with CP. The influence of SPEM improvement on quality of life in a group of severely disabled nonambulant children with CP remains to be assessed.

Clinical relevance of the expression of mRNA of MMP-7, MMP-9, TIMP-1, TIMP-2 and CEA tissue samples from colorectal liver metastases.

BACKGROUND: Nowadays we know that survival rates do not differ between repeated and single liver resections for colorectal liver metastases (CLM). To be able to determine patients prone to early recurrence, the use of different markers with a better prognostic value than the routinely employed tumor markers is required. AIM OF STUDY: The aim of our study was to assess mRNA expression of MMP-7, MMP-9, TIMP-1, TIMP-2 and CEA in tissue samples from CLM and their relationship to disease-free interval (DFI) and overall survival (OS). PATIENTS AND METHODS: The liver tumor biopsies were obtained from 40 patients suffering from CLM treated with radical surgery. mRNA expression levels of CEA, MMPs and TIMPs and a housekeeping gene (GAPDH) were quantified using RT-PCR. RESULTS: The increased expression of CEA, MMP-9 and TIMP-1 in CLM was associated with a short DFI and a high tendency to early CLM recurrence. Statistical analysis confirmed CEA, MMP-9 and TIMP-1 expression as prognostic factors of survival. CONCLUSION: This study demonstrated the importance of CEA, MMP-9 and TIMP-1 in the prognostication of DFI and OS.

Clinicopathological assessment and quantitative estimation of the matrix metalloproteinases MMP-2 and MMP-7 and the inhibitors TIMP-1 and TIMP-2 in colorectal carcinoma tissue samples.

BACKGROUND: The matrix metalloproteinases (MMP) are a family of proteolytic enzymes involved in tumor growth and in the process of invasion. The aim of our study was to test the levels of MMP-2, MMP-7, and the MMP inhibitors TIMP-1 and TIMP-2 mRNA in colorectal carcinoma tissue samples with the clinicopathological status of the disease. PATIENTS AND METHODS: Colorectal carcinoma tissue samples were obtained from 38 patients who underwent resection of colorectal carcinoma. The expression levels of mRNA of MMP-2, MMP-7, TIMP-1, TIMP-2 and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a housekeeping gene were quantified in these tissue samples using the method of reverse transcription real-time PCR. RESULTS: It was found that the levels of mRNA expression of MMP-2, TIMP-2, MMP-7 and TIMP-1 were significantly higher in tumor tissue samples than in the normal colorectal tissue (p < 0.0020, p < 0.0467, p < 0.0007 and p < 0.0003 respectively). The level of mRNA expression of MMP-2, MMP-7, TIMP-2 and TIMP-1 did not correlate with the stage of the disease, localization of the tumor, metastatic spread or with disease-free survival (DFI). We recorded a statistically significant inverse negative correlation (r = -0.85; p < 0.0001) between the levels of MMP-7 mRNA and TIMP-2 mRNA. Correlations between the values of mRNA MMP-7 vs. TIMP-1, MMP-2 vs. TIMP-2, MMP-2 vs. TIMP-1 and MMP-2 vs. MMP-7 were not statistically significant. CONCLUSION: We found that there were statistically significant differences in the levels of MMP-2, MMP-7, TIMP-1, TIMP-2 mRNA between normal colorectal tissue and tumor tissue, but we did not find any statistically significant correlation between mRNA levels of MMP-2, MMP-7, TIMP-1, TIMP-2 expression and localization of tumor, clinical stage or course of disease. We found an inverse negative statistically significant correlation between mRNA levels of MMP-7 and TIMP-2. On the basis of these results the clinical use of this approach to the determination of a prognosis is ambiguous.

CONCENTRATION OF NATURAL RADIONUCLIDES IN PRIVATE DRINKING WATER WELLS.

Water is one of the most important resources for a human being; therefore, its quality should be properly tested. According to Council Directive No. 2013/51/EUROATOM, there shall be established requirements for the general public health protection with regard to radioactive substances in water intended for human consumption. This article summarises measurement results of selected water samples at 444 private drinking water wells, which are not subject to regular inspection in terms of the Czech legislation.

Evaluation of human body irradiation caused by radionuclides deposited in the filtration unit of gas mask.

Radioactive aerosol particles represent a serious risk for people facing the consequences of nuclear accident of any kind. The first responders to emergency situation need to be protected by personal protective equipment which includes radiation protection suit supplemented with gas mask. The purpose of this work is to estimate the dose to the organs of responder's body as a result of radionuclide deposition in the filtration unit of the gas mask. The problem was analyzed using Monte Carlo simulations. The dose absorbed by different organs for five representative radionuclides and the dose distribution over the responder's body are presented in this paper. Based on presented MC simulations, we suggest a method of evaluating the irradiation of the responder by the radionuclides deposited in the filtration unit of the gas mask.

Fluorogenic protein labeling using a genetically encoded unstrained alkene.

We developed a new fluorogenic bioorthogonal reaction that is based on the inverse electron-demand Diels-Alder reaction between styrene (an unstrained alkene) and a simple tetrazine. The reaction forms a new fluorophore with no literature precedent. We have identified an aminoacyl-tRNA synthetase/tRNA pair for the efficient and site-specific incorporation of a styrene-containing amino acid into proteins in response to amber nonsense codon. Fluorogenic labeling of purified proteins and intact proteins in live cells were demonstrated. The fluorogenicity of the styrene-tetrazine reaction can be potentially applied to the study of protein folding and function under physiological conditions with low background fluorescence interference.

Expression of CP4 EPSPS in microspores and tapetum cells of cotton (Gossypium hirsutum) is critical for male reproductive development in response to late-stage glyphosate applications.

Plants expressing Agrobacterium sp. strain CP4 5-enolpyruvylshikimate-3-phosphate synthase (CP4 EPSPS) are known to be resistant to glyphosate, a potent herbicide that inhibits the activity of the endogenous plant EPSPS. The RR1445 transgenic cotton line (current commercial line for Roundup Ready Cotton) was generated using the figwort mosaic virus (FMV) 35S promoter to drive the expression of the CP4 EPSPS gene, and has excellent vegetative tolerance to glyphosate. However, with high glyphosate application rates at developmental stages later than the four-leaf stage (late-stage applications: applications that are inconsistent with the Roundup labels), RR1445 shows male sterility. Another transgenic cotton line, RR60, was generated using the FMV 35S promoter and the Arabidopsis elongation factor-1alpha promoter (AtEF1alpha) for the expression of CP4 EPSPS. RR60 has excellent vegetative and reproductive tolerance to applications of glyphosate at all developmental stages. Histochemical analyses were conducted to examine the male reproductive development at the cellular level of these cotton lines in response to glyphosate applications, and to investigate the correlation between glyphosate injury and the expression of CP4 EPSPS in male reproductive tissues. The expression of CP4 EPSPS in RR60 was found to be strong in all male reproductive cell types. Conversely, CP4 EPSPS expression in RR1445 was low in pollen mother cells, male gametophytes and tapetum, three crucial male reproductive cell types. Our results indicate that the FMV 35S promoter, although expressing strongly in most vegetative tissues in plants, has extremely low activity in these cell types.

Detection of 1,N6-propanodeoxyadenosine in acrolein-modified polydeoxyadenylic acid and DNA by 32P postlabeling.

The interaction of acrolein, an alpha,beta-unsaturated aldehyde, with polydeoxyadenylic acid and DNA has been investigated using 32P-postlabeling analysis. In preliminary experiments, polydeoxyadenylic acid was incubated with excess acrolein and then digested to 3' monophosphates prior to transfer of 32P from [gamma-32P]ATP with T4 polynucleotide kinase. The 3',5'-bisphosphates were 3'-dephosphorylated prior to two-dimensional thin layer chromatography on polyethyleneimine-cellulose layers. Autoradiography provided evidence for the formation of one extra spot of radioactivity, compared to the control. To determine the adduct structure, deoxyadenosine-5'-monophosphate was incubated with a 3-fold excess of acrolein. This material was mixed with a 32P-labeled digest of acrolein-polydeoxyadenylic acid, and the sample was analyzed by ion-pair high performance liquid chromatography. The spot of 32P observed by thin layer chromatography co-eluted with the major product of the acrolein nucleotide reaction mixture, which was purified by ion-pair high performance liquid chromatography. Two-dimensional nuclear magnetic resonance spectroscopy and mass spectrometry showed the adduct to be 3-(2'-deoxyribosyl-5'-monophosphatyl)-7,8,9-trihydro-9-hydro xy- pyrimido[2,3-i]purine(1,N6-propanodeoxyadenosine-5'-monophosphate) . High performance liquid chromatography was used to fractionate digests of acrolein-modified DNA prior to detection of this exocyclic adduct by 32P-postlabeling.

N-acetylgalactosamine glycosylation of MUC1 tandem repeat peptides by pancreatic tumor cell extracts.

Synthetic peptides corresponding to the human mucin MUC1 tandem repeat domain (20 residues) were glycosylated in vitro by using UDP-N-[3H]acetyl-D-galactosamine (GalNAc) and lysates of pancreatic tumor cell lines. Results obtained with peptides of different lengths (from one to five repeats) suggest that increasing the number of tandem repeats has neither a positive nor a negative effect on the density of glycosylation along the MUC1 tandem repeat protein backbone. Purified glycopeptides were sequenced on a gas-phase sequencer, and glycosylated positions were determined by measuring the incorporated radioactivity in fractions collected following each round of Edman degradation. The results showed that two of three threonine residues on the MUC1 tandem repeat peptides were glycosylated by pancreatic tumor cell lysates at the following positons: GVTSAPDTRPAPGSTAPPAH (underlined T indicates position of GalNAc attachment). None of the serine residues were glycosylated. Determination of the mass of the glycopeptides by mass spectrometry confirmed that a maximum of two molecules of GalNAc were covalently linked to each 20-residue repeat unit in the peptides. The data presented here show that acceptor substrate specificity of the UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase detected in lysates of pancreatic and breast tumor cell lines is identical and is limited to some but not all threonines in the MUC1 tandem repeat peptide sequence. The influence of primary amino acid sequence on acceptor substrate activity was evaluated by using several peptides that contain single or double amino acid substitutions (relative to the native human MUC1 sequence). These included substitutions in the residues that were glycosylated and substitutions of the surrounding primary amino acid sequence. The results of these studies suggest that primary amino acid sequence, length, and relative position of the residue to be glycosylated dramatically affect the ability of peptides to serve as acceptor substrates for the UDP-GalNAc:polypeptide N-acetylgalatosaminyltransferase.

Quantitative estimation of matrix metalloproteinases 2 and 7 (MMP-2, MMP-7) and tissue inhibitors of matrix metalloproteinases 1 and 2 (TIMP-1, TIMP-2) in colorectal carcinoma tissue samples.

BACKGROUND: An essential step in the process of tumor invasion and metastasis involves the degradation of tissue barriers in the extracellular matrix (ECM), particularly in the basal membrane (BM). Matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs), in particular MMP-2, MMP-7, TIMP-1 and TIMP-2, play an important role in the process of ECM and BM degradation in connection with tumor invasion. The aim of our study was to assess the levels of MMP-2, MMP-7, TIMP-1 and TIMP-2 mRNA expression in colorectal carcinoma tissue samples and to correlate them with the stage of the disease. PATIENTS AND METHODS: The study included samples of tumor tissue of 38 patients with colorectal carcinoma and samples of tissue of 11 patients with benign disease. The expression levels of mRNA MMP-2, MMP-7, TIMP-1, TIMP-2 and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), as housekeeping gene, were quantified in tissue samples using the method of reverse transcription real-time PCR. RESULTS: The levels of mRNA expression of MMP-2, MMP-7 and TIMP-1 were significantly higher in tumor tissue samples that in the control tissue (p<0.0005, p<0.0007 and p<0.0004). In addition the presence of mRNA MMP-2, MMP-7, TIMP-1 and TIMP-2 in tumor tissue samples in these parameters was significantly higher than in the control tissue (p<0.003, p<0.0001, p<0.0001 and p<0.05). CONCLUSION: This pilot study demonstrated that a significant difference in the level and in the presence of mRNA MMP-2, MMP-7 and TIMP-1 expressions between tumor colorectal and control colorectal tissues might be helpful for the prognosis of colorectal cancer.

Determining radioactive aerosol concentrations using a surface radioactive contamination measurement device.

For experiments with dispersed radioactive aerosols in a radon-aerosol chamber (RAC), it is desirable to know the activity of the radioactive aerosols applied in the RAC. A COLIBRI TTC survey metre with an SABG-15+ probe (Canberra, USA) was purchased for this purpose. The probe is designed for surface contamination measurements, and it is intended to measure the activity of aerosols deposited on the filters during experiments in the RAC. Since the probe is calibrated in a different geometry, its response in the authors' experimental geometry was simulated by a Monte Carlo method. The authors present a Monte Carlo model using MCNPX and an experimental verification of this probe model.

Di-hydrogen contact induced lattice instabilities and structural dynamics in complex hydride perovskites.

The structural phase transitions occurring in a series of perovskite-type complex hydrides based on the tetrahydroborate anion BH4(-) are investigated by means of in situ synchrotron x-ray powder diffraction, vibrational spectroscopy, thermal methods and ab initio calculations in the solid state. Structural dynamics of the BH4 anion are followed with quasi-elastic neutron scattering. We show that unexpected temperature-induced lattice instabilities in perovskite-type ACa(BH4)3 (A = K, Rb, Cs) have their origin in close hydridic di-hydrogen contacts. The rich lattice dynamics lead to coupling between internal B-H vibrations and phonons, resulting in distortions in the high-temperature polymorph that are identical in symmetry to well-known instabilities in oxide perovskites, generally condensing at lower temperatures. It is found that anion-substitution BH4(-) <-> (X = Halide) can relax distortions in ACa(BH4)3 by eliminating coulomb repulsive H(-)···H(-) effects. The interesting nature of phase transition in ACa(BH4)3 enters an unexplored field of weak interactions in ceramic-like host lattices and is the principal motivation for this study. Close di-hydrogen contacts suggest new concepts to tailor crystal symmetries in complex hydride perovskites in the future.

A novel gene expressed in rat ameloblasts codes for proteins with cell binding domains.

Two variants of an mRNA sequence are identified that are expressed at high levels in rat ameloblasts during the formation of the enamel matrix. The sequences contain open reading frames for 407 and 324 amino acid residues, respectively. The encoded proteins, which we call amelins, are rich in proline, glycine, leucine, and alanine residues and contain the peptide domain DGEA, an integrin recognition sequence. The sequences coding for the C-terminal 305 amino acid residues, the 3' nontranslated part, and a microsatellite repeat at the nontranslated 5' region are identical in both mRNA variants. The remaining 5' regions contain 338 nucleotides unique to the long variant, 54 common nucleotides, and 46 nucleotides present only in the short variant. Eleven nucleotides have the potential to code for 5 amino acids of both proteins in different reading frames. The reading frame of the longer variant includes codons for a typical N-terminal signal peptide. The amelins are likely to be constituents of the enamel matrix and the only proteins that have so far been implicated in binding interactions between the ameloblast surface and its extracellular matrix.

Antineoplastic agents. 278. Isolation and structure of axinastatins 2 and 3 from a western Caroline Island marine sponge.

The Republic of Palau marine sponge Axinella sp. was found to be an exceptionally productive source of cell growth inhibitory substances. The strongly antineoplastic polyether macrocyclic lactones halichondrin B (1) and homohalichondrin B (2) were isolated in 1.2 x 10(-6)% and 5.4 x 10(-7)% yields, respectively. In addition to axinastatin 1 (3), two new and cytostatic (GI50 values of 0.35 to 0.0072 microgram/mL against six human cancer cell lines) cycloheptapeptides designated axinastatins 2 (4) and 3 (5) were discovered in 1.4 x 10(-6)% and 1.25 x 10(-6)% yields. Structures were elucidated by high-resolution FABMS and tandem MS/MS techniques augmented by high-field (400 and 500 MHz) 2D-NMR spectral analyses. The absolute configurations were established by a combination of hydrolysis, derivatization, and chiral gas chromatographic methods.

Defining parameters for homology-tolerant database searching.

De novo interpretation of tandem mass spectrometry (MS/MS) spectra provides sequences for searching protein databases when limited sequence information is present in the database. Our objective was to define a strategy for this type of homology-tolerant database search. Homology searches, using MS-Homology software, were conducted with 20, 10, or 5 of the most abundant peptides from 9 proteins, based either on precursor trigger intensity or on total ion current, and allowing for 50%, 30%, or 10% mismatch in the search. Protein scores were corrected by subtracting a threshold score that was calculated from random peptides. The highest (p < .01) corrected protein scores (i.e., above the threshold) were obtained by submitting 20 peptides and allowing 30% mismatch. Using these criteria, protein identification based on ion mass searching using MS/MS data (i.e., Mascot) was compared with that obtained using homology search. The highest-ranking protein was the same using Mascot, homology search using the 20 most intense peptides, or homology search using all peptides, for 63.4% of 112 spots from two-dimensional polyacrylamide gel electrophoresis gels. For these proteins, the percent coverage was greatest using Mascot compared with the use of all or just the 20 most intense peptides in a homology search (25.1%, 18.3%, and 10.6%, respectively). Finally, 35% of de novo sequences completely matched the corresponding known amino acid sequence of the matching peptide. This percentage increased when the search was limited to the 20 most intense peptides (44.0%). After identifying the protein using MS-Homology, a peptide mass search may increase the percent coverage of the protein identified.

Determination of structure and properties of modified chlorophylls by using fast atom bombardment combined with tandem mass spectrometry.

Tandem mass spectrometry (MS/MS) was used to investigate and compare the decompositions of radical cations (M(+.)), radical anions (M(-.)), [M + H](+) ions, and [M + Cat](+) ions (Cat = alkali metal ions) of chlorophylls. Included in this study are chlorophyll a, chlorophyll b, bacteriochlorophyll a, chlorophyll a allomers, and the corresponding pheophytins. Fast atom bombardment of chlorophyll a produces abundant M(+.) ions, which decompose metastably and upon collisional activation to give fragment ions from losses of the phytyl chain and the ß-keto group of ring V. In addition, previously unreported charge-remote fragmentations are useful for identification of branch points on the phytyl chain. Collisional activation of [M + Cat](+) ions produces fragment ions that are complementary to those of the M(+) and are used to examine the intrinsic gas-phase reactivity of metal ions and chlorophylls. Peripheral metal ion attachment in chlorophyll a in the gas phase is suggested to be at C-9, and the ß-keto ester group at C-10, of ring V. Examination of decompositions of chlorophyll dimers suggests that in the gas phase the interaction between monomers involves bonding of the Mg atom of one chlorophyll a molecule and the C-9 carbonyl oxygen of the other, which was also suggested for chlorophyll a dimers in solution.