Laser spectroscopy for breath analysis : towards clinical implementation

Detection and analysis of volatile compounds in exhaled breath represents an attractive tool for monitoring the metabolic status of a patient and disease diagnosis, since it is non-invasive and fast. Numerous studies have already demonstrated the benefit of breath analysis in clinical settings/applications and encouraged multidisciplinary research to reveal new insights regarding the origins, pathways, and pathophysiological roles of breath components. Many breath analysis methods are currently available to help explore these directions, ranging from mass spectrometry to laser-based spectroscopy and sensor arrays. This review presents an update of the current status of optical methods, using near and mid-infrared sources, for clinical breath gas analysis over the last decade and describes recent technological developments and their applications. The review includes: tunable diode laser absorption spectroscopy, cavity ring-down spectroscopy, integrated cavity output spectroscopy, cavity-enhanced absorption spectroscopy, photoacoustic spectroscopy, quartz-enhanced photoacoustic spectroscopy, and optical frequency comb spectroscopy. A SWOT analysis (strengths, weaknesses, opportunities, and threats) is presented that describes the laser-based techniques within the clinical framework of breath research and their appealing features for clinical use.Peer reviewe

The widening spectrum of C9ORF72-related disease; genotype/phenotype correlations and potential modifiers of clinical phenotype

The GGGGCC (G4C2) repeat expansion in C9ORF72 is the most common cause of familial amyotrophic lateral sclerosis (ALS), frontotemporal lobar dementia (FTLD) and ALS–FTLD, as well as contributing to sporadic forms of these diseases. Screening of large cohorts of ALS and FTLD cohorts has identified that C9ORF72-ALS is represented throughout the clinical spectrum of ALS phenotypes, though in comparison with other genetic subtypes, C9ORF72 carriers have a higher incidence of bulbar onset disease. In contrast, C9ORF72-FTLD is predominantly associated with behavioural variant FTD, which often presents with psychosis, most commonly in the form of hallucinations and delusions. However, C9ORF72 expansions are not restricted to these clinical phenotypes. There is a higher than expected incidence of parkinsonism in ALS patients with C9ORF72 expansions, and the G4C2 repeat has also been reported in other motor phenotypes, such as primary lateral sclerosis, progressive muscular atrophy, corticobasal syndrome and Huntington-like disorders. In addition, the expansion has been identified in non-motor phenotypes including Alzheimer’s disease and Lewy body dementia. It is not currently understood what is the basis of the clinical variation seen with the G4C2 repeat expansion. One potential explanation is repeat length. Sizing of the expansion by Southern blotting has established that there is somatic heterogeneity, with different expansion lengths in different tissues, even within the brain. To date, no correlation with expansion size and clinical phenotype has been established in ALS, whilst in FTLD only repeat size in the cerebellum was found to correlate with disease duration. Somatic heterogeneity suggests there is a degree of instability within the repeat and evidence of anticipation has been reported with reducing age of onset in subsequent generations. This variability/instability in expansion length, along with its interactions with environmental and genetic modifiers, such as TMEM106B, may be the basis of the differing clinical phenotypes arising from the mutation

Structural and functional analyses of the interaction of archaeal RNA polymerase with DNA.

Multi-subunit RNA polymerases (RNAPs) in all three domains of life share a common ancestry. The composition of the archaeal RNAP (aRNAP) is not identical between phyla and species, with subunits Rpo8 and Rpo13 found in restricted subsets of archaea. While Rpo8 has an ortholog, Rpb8, in the nuclear eukaryal RNAPs, Rpo13 lacks clear eukaryal orthologs. Here, we report crystal structures of the DNA-bound and free form of the aRNAP from Sulfolobus shibatae. Together with biochemical and biophysical analyses, these data show that Rpo13 C-terminus binds non-specifically to double-stranded DNA. These interactions map on our RNAP-DNA binary complex on the downstream DNA at the far end of the DNA entry channel. Our findings thus support Rpo13 as a RNAP-DNA stabilization factor, a role reminiscent of eukaryotic general transcriptional factors. The data further yield insight into the mechanisms and evolution of RNAP-DNA interaction

Optical nonlinearity and piezoelectricity in 2,4,6-trimethylpyridinium perchlorate

[(CH3)(3)C5H2NH][ClO4] exhibits rich polymorphism, it undergoes four structural phase transitions: from phases I to II at 356/327 K ( heating/cooling), II-III at 346/326, III-IV at 226 K and IV-V at 182/170 K. [(CH3)(3)C5H2NH][ClO4] reveals a strong optical nonlinearity over a wide temperature region with the SHG efficiency comparable to that of KDP. The piezoelectric properties were studied macroscopically by series resonance method over the phases III, IV and V as well as microscopically by means of piezoelectric force microscopy ( PFM) in ambient conditions. One of the piezoelectric module at phase transition point at 226 K drops to the value twice smaller than in room temperature what up to now was not encountered in literature. Moreover the ferroelastic phase transition IV-V was observed by means of polarizing optical microscope. The choice of the point group of phase I (Pmmm) was confirmed by the SHG measurements. The updated phase diagram is presented.M.W. acknowledges the support of a research fellowship from the Polish Ministry of Science and Higher Education, Grant No. 657/MOB/2011/0.info:eu-repo/semantics/publishedVersio