Peak Height Ratio Research Articles

A novel FTA™ elute card collection method that improves direct DNA amplification from bloodstained concrete

Concrete is a common construction material found in residential and commercial buildings, bridges and parking lots that is a composite matrix containing aggregate held together with cement. The porous nature of concrete can make the collection and genotyping of biological fluids, such as blood, challenging. Forensic evidence can become embedded within the matrix, potentially reducing the amount of DNA available for analysis. In forensic science, “direct” amplification refers to a genotyping method that amplifies a DNA profile directly from a sample without DNA extraction, saving time and money. We investigated a novel application of Whatman™ FTA™ Elute cards in their ability to directly amplify PowerPlex® Fusion and Y23 profiles from minute amounts of blood that had been deposited on different concrete structures. In comparison to traditional collection methods, directly profiling blood stained construction materials using FTA™ Elute cards increased the percentage loci amplified and significantly improved both allele peak height and peak height ratio while reducing allelic drop-out. FTA™ Elute cards can provide a reliable, inexpensive and superior alternative to traditional methods.

Quantifying collagen quality in archaeological bone: Improving data accuracy with benchtop and handheld Raman spectrometers

Chemical analysis of collagen and other endogenous protein in excavated bones is ever more common in paleontology and archaeology to determine dietary ecology, migration patterns, age, and diagenetic pathways. Decisions to sacrifice valuable samples to destructive stable isotope, radiogenic isotope, and proteomic analyses are easier to make if one knows ahead of time whether sufficient undegraded organic material is preserved in the bone for chemical analysis. Recent advances with near–infrared Raman spectroscopy to non-destructively pre-screen bones for the presence of undegraded endogenous protein can indicate whether original isotopic or proteomic signatures have remained intact in long-buried bones. However, it is crucial to examine the different emerging approaches with benchtop and handheld Raman spectrometers and to establish uniform data reporting standards that will allow laboratories to accurately compare results. Three recently published studies are compared to understand the factors that affect protein screening success and to establish best practices for the technique in the laboratory and in the field. A set of 37 archaeological human bone samples analyzed previously by the authors using FT-Raman spectroscopy are re-analyzed with a handheld 1064nm Raman spectrometer such that the laser power was similar but the spectral resolution and signal-to-noise were lower. Two methods to identify peak heights were evaluated: 1) peak height fixed at a specific wavenumber and baseline anchored at fixed points bracketing the band and 2) averaging peak intensities over a short wavenumber range while also setting the baseline of the band by an average of several anchor points. This second method appeared to better classify whether the bones contained well-preserved protein signatures. In particular, peak height ratios of 960cm−1 to 1636cm−1 or 1450cm−1 can indicate quality and abundance of bone protein, but have benefits and trade-offs that depend on the instrument used. The 960cm−1:1636cm−1 ratio is more descriptive of collagen quality as defined by an extracted carbon:nitrogen ratio of 2.8–3.6, but the 1636cm−1 peak can be difficult to resolve well with an inherently less sensitive handheld Raman spectrometer. The 1450cm−1 peak is more prominent in the spectrum and therefore more easily resolved with a handheld spectrometer, but it describes a common CH stretch found in collagen and other organic molecules.

New cellulose crystallinity estimation method that differentiates between organized and crystalline phases

A new method is proposed for estimation of cellulose crystallinity (CrI) based on 93 cm−1 Raman band in spectra of cellulose I materials. In this method (93-Raman), CrI was determined based on regression that was developed using the ratios of peak-heights of the 93 and 1096 cm−1 Raman bands (I93/I1096). For calibration purposes, a set of eight samples, all derived from cotton microcrystalline cellulose Whatman CC31 were selected. When the peak intensity ratios (I93/I1096) were plotted against the calculated CrIs of the calibration set samples, the plot showed an excellent linear correlation (R2 = 0.9888). The 93-Raman method was used to estimate crystallinities of a number of cellulose materials including poplar wood samples that were hydrothermally treated at various temperatures. The wood 93-Raman CrI data showed that the method is able to differentiate between organized and crystalline phases of cellulose, a capability lacking in many other CrI estimation methods.

Influence of soil γ-irradiation and spiking on sorption of p,p′-DDE and soil organic matter chemistry

The fate of organic chemicals and their metabolites in soils is often investigated in model matrices having undergone various pre-treatment steps that may qualitatively or quantitatively interfere with the results. Presently, effects associated with soil sterilization by γ-irradiation and soil spiking using an organic solvent were studied in one freshly spiked soil (sterilization prior to contamination) and its field-contaminated (sterilization after contamination) counterpart for the model organic compound 1,1-Dichloro-2,2-bis(4-chlorophenyl)ethene (p,p′-DDE). Changes in the sorption and potential bioavailability of spiked and native p,p′-DDE were measured by supercritical fluid extraction (SFE), XAD-assisted extraction (XAD), and solid-phase microextraction (SPME) and linked to qualitative changes in soil organic matter (SOM) chemistry measured by diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy. Reduced sorption of p,p´-DDE detected with XAD and SPME was associated more clearly with spiking than with sterilization, but SFE showed a negligible impact. Spiking resulted in an increase of the DRIFT-derived hydrophobicity index, but irradiation did not. Spectral peak height ratio descriptors indicated increasing hydrophobicity and hydrophilicity in pristine soil following sterilization, and a greater reduction of hydrophobic over hydrophilic groups as a consequence of spiking. In parallel, reduced sorption of p,p´-DDE upon spiking was observed. Based on the present samples, γ-irradiation appears to alter soil sorptive properties to a lesser extent when compared to common laboratory processes such as spiking with organic solvents.

A quantification method for peroxyacetyl nitrate (PAN) using gas chromatography (GC) with a non-radioactive pulsed discharge detector (PDD)

In this study, we developed a method for continuous PAN measurements by gas chromatography (GC) with a non-radioactive pulsed discharge detector (PDD). Operational parameters were optimized based on the ratio of peak height over baseline noise (P/N ratio). The GC/PDD system was compared with a traditional radioactive electron-capture detector (ECD). In the lab, the method detection limit (MDL) of the new GC/PDD method (9 pptv) was lower than the radioactive GC/ECD method (15 pptv), demonstrating its excellent potential. The MDL of GC/PDD in the field campaign at the Mt. Bachelor Observatory (MBO) was 23 pptv, higher than in the lab. This was caused in part by the decreased slope of the calibration curve resulting from the low air pressure level at MBO. However, the MDL level of GC/PDD at MBO is still low enough for accurate PAN measurements, although special attention should be paid to its application at high-elevation sites. Observations of PAN were conducted at MBO in the summer of 2016 with the GC/PDD system, and provided more evidence of the performance of the system. PAN was found to be highly correlated with CO. The promising performance of GC/PDD which does not require a radioactive source makes it a useful approach for accurate PAN measurements in the field.

Quantitative Raman spectroscopic study of the H2─CH4 gaseous system

AbstractThe Raman spectra of pure H2 and CH4 gases and their 5 gaseous mixtures were collected at pressures from 1 to 40 MPa at ambient temperature. They were systematically analyzed in order to establish methodology for quantitative determination of composition and pressure of H2─CH4 bearing fluid inclusions. The peak positions of 4 vibrational bands of H2 in pure H2 gas decrease first and then increase after reaching their minima values at about 30 MPa. The wavenumbers of ʋ1 band of CH4 in pure CH4 gas decreases in wavenumber monotonically in the entire investigated pressure range. In H2─CH4 gaseous mixtures, both the peak positions of H2 and CH4 shift to lower wavenumbers with increasing pressure. The peak positions of ʋ1 band of CH4 can be used to determine the pressure of pure CH4 and CH4‐dominated fluids, where the peak position shifts are sufficiently large for precise pressure determination. The peak widths of H2 and CH4 in pure H2 and CH4 gases and H2─CH4 gaseous mixtures broaden as pressure increases. The peak area ratios and the peak height ratios between CH4 and H2 in H2─CH4 binary mixtures are sensitive to composition (i.e., molar ratio between CH4 and H2) but are almost independent of pressure. Thus, the peak area or peak height ratios can be used to determine the composition of H2─CH4 fluids. On the other hand, the peak height ratios of Q1(1) to Q1(3) bands in pure H2 gas or H2‐dominated gaseous mixtures are sensitive to pressure and insensitive to composition. Therefore, in H2‐dominated fluids, the relative peak heights of Q1(1) and Q1(3) of H2 is a better alternative for pressure determination. Based on our established Raman quantitative analysis method, we determined the composition and internal pressure of a natural H2─CH4‐bearing melt inclusion in quartz from Jiajika granite.

Probing electron-hole components of subgap states in Coulomb blockaded Majorana islands

Recent tunneling spectroscopy experiments in semiconducting nanowires with proximity-induced superconductivity have reported robust zero-bias conductance peaks. Such a feature can be compatible with the existence of topological Majorana bound states (MBSs) and with a trivial Andreev bound state (ABS) near zero energy. Here, we argue that additional information, that can distinguish between the two cases, can be extracted from Coulomb-blockade experiments of Majorana islands. The key is the ratio of peak heights of consecutive conductance peaks give information about the electron and hole components of the lowest-energy subgap state. In the MBS case, this ratio goes to one half for long wires, while for short wires with finite MBS overlap it oscillates a function of Zeeman energy with the same period as the MBS energy splitting. We explain how the additional information might help to distinguish a trivial ABS at zero energy from a true MBS and show case examples.

Degree of conversion and depth of cure of Ivocerin containing photo-polymerized resin luting cement in comparison to conventional luting agents.

Objective:To evaluate the degree of conversion (DC) and depth (extent) of cure of four resin cements (Variolink E, Calibra, NX3 and Variolink N) using Fourier transform infrared (FTIR) and Vickers Micro hardness (MH).Methods:Ten disks (1mmx2mm) of each resin cement were light cured through a ceramic disk for 40 seconds prior to assessment. The ATR spectra of the uncured resin were collected in absorbance mode from 16 scans at 4 wave number resolutions. Degree of conversion was calculated by estimating the changes in peak height ratio of the absorbance intensities of aliphatic C=C peak at 1638 cm-1 and that of an internal standard peak of aromatic C=C at 1608 cm-1 during polymerization. For Vickers microhardness testing 10 disks of each cement specimen was exposed to 100 grams of load for 15 seconds. Three indentations were made 0.5mm apart and an average Vickers micro-hardness (MH) for each specimen. Two way ANOVA and multiple comparison tests were performed to assess data.Results:The highest degree of conversion by peak area was shown by Variolink-Esthetic [light-cure (87.18±2.90%)]; however the lowest was observed in samples of Variolink-N [Dual cure (44.55±4.33%)]. Similarly, Variolink-Esthetic and NX3 cement showed significantly higher MH as compared to other groups.Conclusion:Ivocerin containing Variolink–E cement showed high degree of conversion and extent of polymerization when compared to conventional light and dual cure luting cements.

Inoculation and co-inoculation of alfalfa seedlings with root growth promoting microorganisms (Piriformospora indica, Glomus intraradices and Sinorhizobium meliloti) affect molecular structures, nutrient profiles and availability of hay for ruminants.

Inoculation of alfalfa seedlings with root growth promoting microorganisms under semi-arid climate condition may improve biomass production and nutritive value. The current study aimed to investigate the effect of inoculation of alfalfa seedlings with Piriformospora indica (Pi) and co-inoculating Pi with Glomus intraradices (Gi + Pi) or Sinorhizobium meliloti (Sm + Pi) on hay yield, chemical composition, molecular structures by Fourier transformed infrared (FTIR) spectroscopy, in situ ruminal degradability and in vitro gas production. Seedlings were grown in experimental pots in a greenhouse until first cut and then transferred outside and cut a further 4 times. Biomass yield was similar across the treatments. Acid detergent fiber (ADF) concentration was higher in Pi than in control hay, and ADF decreased further with co-inoculation (P < 0.05). The ether extract (EE) concentration was lower for Pi and Gi + Pi compared with control hay, and control, Pi and Gi + Pi hays had lower EE concentration compared with Sm + Pi (P < 0.05). The FTIR spectroscopic vibration peak height ratio related to proteins (amide 1 + amide 2): total carbohydrate ratio was lower for the inoculation treatments compared with control hay (P < 0.05). In situ ruminal degradability of dry matter and organic matter were higher for hay of inoculated and co-inoculated seedlings than for control hay (P < 0.05). In conclusion, hay of alfalfa seedlings inoculated and co-inoculated with root growth promoting microorganisms had improved nutritional value compared with hay from non-treated alfalfa seedlings, and co-inoculation was the most effective, however, changes were relatively minor.

Dual-Emitting Dye@MOF Composite as a Self-Calibrating Sensor for 2,4,6-Trinitrophenol.

An anionic metal-organic framework (MOF) {(NH2Me2)[Zn3(μ3-OH)(tpt)(TZB)3](DMF)12}n (1, tpt = 2,4,6-tri(4-pyridyl)-1,3,5-triazine, H2TZB = 4-(1H-tetrazol-5-yl)benzoic acid and DMF = N,N-dimethylformamide), with both nanosized cages and partitions, has been solvothermally synthesized, which can serve as a crystalline vessel to encapsulate the fluorescent dye rhodamine 6G (Rh6G) via a "bottle around ship" approach. As a result, the obtained dye@MOF composite system features a blue emission of the ligand at 373 nm and a red emission of Rh6G at 570 nm when dispersed in solution, which could be used for decoding the trace amount of 2,4,6-trinitrophenol (TNP) by referring the peak-height ratio of each emission, even in coexistence with other potentially competitive nitroaromatic analytes. Furthermore, the observed fluorescence responses of the composite toward TNP are highly stable and reversible after recycling experiments. To the best of our knowledge, this is the first example of an MOF-implicated self-calibrated sensor for TNP detection.

A new mathematical model of wrist pulse waveforms characterizes patients with cardiovascular disease – A pilot study

The purpose of this study was to analyze and compare a series of measured radial pulse waves as a function of contact pressure for young and old healthy volunteers, and old patients with cardiovascular disease. The radial pulse waves were detected with a pressure sensor and the contact pressure of the sensor was incremented by 20gf during the signal acquisition. A mathematical model of radial pulse waveform was developed by using two Gaussian functions modulated by radical functions and used to fit the pulse waveforms. Then, a ratio of area (rA) and a ratio of peak height (rPH) between percussion wave and dicrotic wave as a function of contact pressure were calculated based on fitted parameters. The results demonstrated that there was a maximum for waveform peak height, a minimum for rA (rAmin) and a minimum for rPH (rPHmin) appeared as contact pressure varied. On average, older patients had higher peak amplitude and a significantly smaller rAmin (p<0.001) and rPHmin (p<0.02) than the young and old volunteers. The rAmin and rPHmin calculated with the mathematical model had moderate to strong positive linear correlations (r=0.66 to 0.84, p<0.006) with those directly calculated without the model. The receiver operating characteristic (ROC) analysis showed that the rAmin calculated with the model and the contact pressure measured at the rAmin had good diagnostic accuracy to distinguish healthy volunteers vs. diseased patients. Therefore, using the mathematical model to quantitatively analyze the radial pulse waveforms as a function of contact pressure could be useful in the diagnosis of cardiovascular diseases.

Detection of EGFR mutation in plasma using multiplex allele-specific PCR (MAS-PCR) and surface enhanced Raman spectroscopy

In this study, surface enhanced Raman spectroscopy (SERS) in combination with multiplexed polymerase chain reaction (PCR) was utilized to detect mutations of exons 19 and 21 of the epidermal growth factor receptor (EGFR) gene. Through the use of multiplexed PCR, the two mutation types were amplified in a single reaction. SERS was used on the PCR products to detect mutations. DNA mixtures with increasing mutation percentages showed good linear relationship between mutation rates and peak height. Then, this PCR-SERS method was used on the plasma of 48 patients with non-small cell lung cancer (NSCLC) to detect EGFR mutations. Analysis of variance (ANOVA) and receiver operating characteristic (ROC) analysis revealed that the peak height ratios were significant for identifying different mutation types. The specificity, sensitivity and accuracy obtained were all 100%. The proposed method was then validated through comparison with high resolution melting (HRM) and showed high concordance with HRM (Pearson correlation is 0.92). Finally, logistic regression was performed on EGFR mutation status and the clinical features of the 48 patients. Our study indicates that PCR-SERS is an effective, noninvasive, and economical method for the detection and monitoring of EGFR mutations in the plasma of patients with NSCLC.

Alternate injections coupled with flow-gated capillary electrophoresis for rapid and accurate quantitative analysis of urine samples

Capillary electrophoresis (CE) is a powerful separation technique with advantages over HPLC in terms of separation efficiency, speed, and cost. However, CE suffers in poor reproducibility in quantitative chemical analysis, which is one of major drawbacks preventing its widespread use in routine analytical laboratories. Here we report a novel strategy to enhance the quantitative capability of flow-gated CE. The platform integrated dual flow branches to respectively supply a sample and its standard additions that were then alternately injected into a single capillary for rapid separations (typically 20–90 s). A micro-fabricated switch was used to enable the alternate injections. It was assumed that the analytical system maintained constant conditions during neighboring injections that served as external self-standards for quantitation. This strategy was expected to reduce uncertainties caused by the fluctuation in capillary conditions and the drift of detection systems. Experimental results demonstrated that the dual-branch flow-gated CE coupled with alternate injections significantly improved the reproducibility with respect to peak height ratios under deliberate variations in injection volumes, separation voltages, optical focusing, and laser power; and thus the interday precision was ensured. To demonstrate its applicability, cyanide and amino acids in human urine were quantified rapidly with the one-point standard addition method after fluorogenic derivatization with naphthalene-2,3-dicarboxaldehyde (NDA), and the measurement accuracy was validated by determining the recovery of standard cyanide added to a urinary matrix. This strategy would be valuable to enable the quantitative capability of flow-gated CE in the measurements of a broad range of analytes, especially those lacking suited internal standards.

Fully automated atlas‐based method for prescribing 3D PRESS MR spectroscopic imaging: Toward robust and reproducible metabolite measurements in human brain

To implement a fully automated atlas-based method for prescribing 3D PRESS MR spectroscopic imaging (MRSI). The PRESS selected volume and outer-volume suppression bands were predefined on the MNI152 standard template image. The template image was aligned to the subject T1 -weighted image during a scan, and the resulting transformation was then applied to the predefined prescription. To evaluate the method, H-1 MRSI data were obtained in repeat scan sessions from 20 healthy volunteers. In each session, datasets were acquired twice without repositioning. The overlap ratio of the prescribed volume in the two sessions was calculated and the reproducibility of inter- and intrasession metabolite peak height and area ratios was measured by the coefficient of variation (CoV). The CoVs from intra- and intersession were compared by a paired t-test. The average overlap ratio of the automatically prescribed selection volumes between two sessions was 97.8%. The average voxel-based intersession CoVs were less than 0.124 and 0.163 for peak height and area ratios, respectively. Paired t-test showed no significant difference between the intra- and intersession CoVs. The proposed method provides a time efficient method to prescribe 3D PRESS MRSI with reproducible imaging positioning and metabolite measurements. Magn Reson Med 79:636-642, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Competitive PCR-High Resolution Melting Analysis (C-PCR-HRMA) for large genomic rearrangements (LGRs) detection: A new approach to assess quantitative status of BRCA1 gene in a reference laboratory

Aim of the studyEvaluation of copy number variation (CNV) in BRCA1/2 genes, due to large genomic rearrangements (LGRs), is a mandatory analysis in hereditary breast and ovarian cancers families, if no pathogenic variants are found by sequencing. LGRs cannot be detected by conventional methods and several alternative methods have been developed. Since these approaches are expensive and time consuming, identification of alternative screening methods for LGRs detection is needed in order to reduce and optimize the diagnostic procedure. The aim of this study was to investigate a Competitive PCR-High Resolution Melting Analysis (C-PCR-HRMA) as molecular tool to detect recurrent BRCA1 LGRs. Material and methodsC-PCR-HRMA was performed on exons 3, 14, 18, 19, 20 and 21 of the BRCA1 gene; exons 4, 6 and 7 of the ALB gene were used as reference fragments. ResultsThis study showed that it is possible to identify recurrent BRCA1 LGRs, by melting peak height ratio between target (BRCA1) and reference (ALB) fragments. Furthermore, we underline that a peculiar amplicon-melting profile is associated to a specific BRCA1 LGR. All C-PCR-HRMA results were confirmed by Multiplex ligation-dependent probe amplification. ConclusionsC-PCR-HRMA has proved to be an innovative, efficient and fast method for BRCA1 LGRs detection. Given the sensitivity, specificity and ease of use, c-PCR-HRMA can be considered an attractive and powerful alternative to other methods for BRCA1 CNVs screening, improving molecular strategies for BRCA testing in the context of Massive Parallel Sequencing.

Thermodynamic and kinetic modeling of grain boundary equilibrium segregation of P in α-Fe

Phosphorus is a primary contributor to interface fracture and embrittlement in steels because of its strong segregation tendency at grain boundaries (GBs). The lack of consistency in literature data imposes great difficulties in performing segregation modeling that is compatible with both the Langmuir-Mclean segregation theory and the thermodynamic description of the Bcc(Fe,P) phase. This work carefully evaluated experimental data for phosphorus segregation at GBs in α-Fe and provided a new formula for converting the auger electron spectroscopy (AES) peak height ratio to GBs. Based on newly assessed literature data, this work proposes that the major driving force for phosphorus segregation is the formation of Fe3P-type clusters at GBs, which is supported not only by the almost equivalent Gibbs energy of α_Fe using the Bcc(Fe,P) substitutional model and the Bcc(Fe,Fe3P, P) associate model, but also by the good agreement between thermodynamic/kinetic modeling results and experimental data.

Internal validation of the DNAscan/ANDE™ Rapid DNA Analysis™ platform and its associated PowerPlex® 16 high content DNA biochip cassette for use as an expert system with reference buccal swabs

Rapid DNA platforms are fully integrated systems capable of producing and analyzing short tandem repeat (STR) profiles from reference sample buccal swabs in less than two hours. The technology requires minimal user interaction and experience making it possible for high quality profiles to be generated outside an accredited laboratory. The automated production of point of collection reference STR profiles could eliminate the time delay for shipment and analysis of arrestee samples at centralized laboratories. Furthermore, point of collection analysis would allow searching against profiles from unsolved crimes during the normal booking process once the infrastructure to immediately search the Combined DNA Index System (CODIS) database from the booking station is established. The DNAscan/ANDE™ Rapid DNA Analysis™ System developed by Network Biosystems was evaluated for robustness and reliability in the production of high quality reference STR profiles for database enrollment and searching applications. A total of 193 reference samples were assessed for concordance of the CODIS 13 loci. Studies to evaluate contamination, reproducibility, precision, stutter, peak height ratio, noise and sensitivity were also performed. The system proved to be robust, consistent and dependable. Results indicated an overall success rate of 75% for the 13 CODIS core loci and more importantly no incorrect calls were identified. The DNAscan/ANDE™ could be confidently used without human interaction in both laboratory and non-laboratory settings to generate reference profiles.

Enhanced Alignment of Water-Soluble Polythiophene Using Cellulose Nanocrystals as a Liquid Crystal Template.

Cellulose nanocrystals (CNCs) are bioderived, rodlike particles that form a chiral nematic liquid crystal (LC) in water. In this work, CNCs were used to induce long-range order in a semiconducting polymer, poly[3-(potassium-4-butanoate) thiophene-2,5-diyl] (PPBT). When mixed with CNCs, it was found that PPBT was incorporated into the liquid crystal "template" to form ordered structures with highly birefringent domains, as observed under polarized light. We show that the π-π interactions between polymer chains, which contribute considerably to the energetics of the semiconducting system, are directly influenced by the presence and packing of the liquid crystal phase. Upon increasing the concentration of CNCs from the isotropic to chiral nematic regime, we observe a bathochromic shift in the UV-vis spectra and the emergence of the 0-0 vibrational peak, suggesting enhanced π-π stacking leading to chain coplanarization. Furthermore, the chiral nature of the PPBT/CNC mixture was evidenced by a negative peak in circular dichroism (CD) spectroscopy, promoting the notion that the polymer chains followed the helicoidal twist of the chiral nematic liquid crystal host. At high temperatures, the peak height ratios and overall intensities of the UV-vis and CD spectra associated with PPBT decreased as the chiral nematic pitch grew larger in size.

Research on Modulation Frequency and Scanning Frequency Parameters Selection of TDLAS System

The modulation frequency and scanning frequency effect on the detection signal of tunable diode laser absorption spectroscopy (TDLAS) system is studied. The experiment system is designed to detect carbon dioxide (CO2). This paper analyzes the relationship between scanning frequency and modulation frequency and researches correlation theory. When modulation frequency and scanning frequency take different values, the change of the second harmonic (2f) signal waveform, maximum amplitude, signal-to-noise ratio (SNR), peak width and peak height ratio (PHR) are studied by experiment. It provides the theory and experiment basis for the selection of two parameters of TDLAS harmonic detection method.

Developmental and internal validation of a novel 13 loci STR multiplex method for Cannabis sativa DNA profiling

Marijuana (Cannabis sativa L.) is a plant cultivated and trafficked worldwide as a source of fiber (hemp), medicine, and intoxicant. The development of a validated method using molecular techniques such as short tandem repeats (STRs) could serve as an intelligence tool to link multiple cases by means of genetic individualization or association of cannabis samples. For this purpose, a 13 loci STR multiplex method was developed, optimized, and validated according to relevant ISFG and SWGDAM guidelines. The STR multiplex consists of 13 previously described C. sativa STR loci: ANUCS501, 9269, 4910, 5159, ANUCS305, 9043, B05, 1528, 3735, CS1, D02, C11, and H06. A sequenced allelic ladder consisting of 56 alleles was designed to accurately genotype 101 C. sativa samples from three seizures provided by a U.S. Customs and Border Protection crime lab. Using an optimal range of DNA (0.5-1.0ng), validation studies revealed well-balanced electropherograms (inter-locus balance range: 0.500-1.296), relatively balanced heterozygous peaks (mean peak height ratio of 0.83 across all loci) with minimal artifacts and stutter ratio (mean stutter of 0.021 across all loci). This multi-locus system is relatively sensitive (0.13ng of template DNA) with a combined power of discrimination of 1 in 55 million. The 13 STR panel was found to be species specific for C. sativa; however, non-specific peaks were produced with Humulus lupulus. The results of this research demonstrate the robustness and applicability of this 13 loci STR system for forensic DNA profiling of marijuana samples.