Differences In Peak Intensities Research Articles

Application of isotopic labeling, and gas chromatography mass spectrometry, to understanding degradation products and pathways in the thermal-oxidative aging of Nylon 6.6

Abstract Nylon 6.6 containing 13C isotopic labels at specific positions along the macromolecular backbone has been subjected to extensive thermal-oxidative aging at 138 °C for time periods up to 243 days. In complementary experiments, unlabeled Nylon 6.6 was subjected to the same aging conditions under an atmosphere of 18O2. Volatile organic degradation products were analyzed by cryofocusing gas chromatography mass spectrometry (cryo-GC/MS) to identify the isotopic labeling. The labeling results, combined with basic considerations of free radical reaction chemistry, provided insights to the origin of degradation species, with respect to the macromolecular structure. A number of inferences on chemical mechanisms were drawn, based on 1) the presence (or absence) of the isotopic labels in the various products, 2) the location of the isotope within the product molecule, and 3) the relative abundance of products as indicated by large differences in peak intensities in the gas chromatogram. The overall degradation results can be understood in terms of free radical pathways originating from initial attacks on three different positions along the nylon chain which include hydrogen abstraction from: the (CH2) group adjacent to the nitrogen atom, at the (CH2) adjacent the carbonyl group, and direct radical attack on the carbonyl. Understanding the pathways which lead to Nylon 6.6 degradation ultimately provides new insight into changes that can be leveraged to detect and reduce early aging and minimize problems associated with material degradation.

Peptide‐Based Biomarker Discovery for Identification of Rice Cultivars using Surface Enhanced Laser Desorption/Ionization Time‐of‐Flight Mass Spectrometry

ABSTRACTBiomarkers of desirable traits are important for selection of elite lines in multigeneration breeding processes. To develop peptide‐based biomarkers for rice (Oryza sativa L.) genotype identification, we applied surface enhanced laser desorption/ionization (SELDI) time‐of‐flight (TOF), a mass spectrometry (MS) technique. Dehusked rice of ‘Ilpumbyeo’ was compared with two rice cultivars, Goami‐2, which was mutagenized for development of high amylose and selected from Ilpumbyeo, and Goami‐3, which originated from Goami‐2. In the molecular range from 2000 to 25,000 Da, the three cultivars exhibited significant differences in peak intensity (p < 0.01) for 13 peptides on CM10 (weak cation exchange) and 31 peptides on Q10 (strong anion exchange). Heat mapping via supervised hierarchical clustering on the peptides showing significant differences between the three cultivars at p < 0.01 effectively distinguished cultivars and categorized these peptides into seven groups. Considering the peaks with high intensity and low probability among the cultivars, peptides of 2621, 3498, 3801, and 7854 Da for Ilpumbyeo, those of 7547 and 8889 Da for Goami‐2, and that of 11,560 Da for Goami‐3 were selected as potential biomarkers for rice genotype identification. Our work suggests that distinguished peptides of rice cultivars could be detected using SELDI‐TOF MS, which has advantages in profiling of low molecular peptides, and used as biomarkers for cultivar identification.

Characterization of Active Species in Cu-Beta Zeolite by Temperature-Programmed Reduction Mass Spectrometry (TPR-MS)

The number and type of copper species present in an under-exchanged Cu-Beta zeolite catalyst were characterized using temperature-programmed reduction mass spectrometry (TPR-MS). Both H2 consumption and H2O evolution were tracked, yielding additional insights into the nature of Cu species. Prior to the TPR-MS tests, catalyst samples were subjected to various high- temperature aging treatments in the presence of O2 in He, in order to assist with interrogating and resolving different types of sites. Absence of reducible species in the precursor material was confirmed by subjecting the H-form of the same zeolite to the TPR. Upon aging at temperatures below 700 °C, the TPR pattern showed several distinct peaks of different intensities. Aging at 800 °C led to shifting and broadening of these H2 consumption peaks, as well as to some reduction of the integral amount of the reducible sites. The 900 °C exposure resulted in a drastic change of the TPR pattern, with several new well-resolved H2 consumption peaks, indicative of drastic changes in the catalyst structure. The integral amount of H2 consumed quantitatively matched the amount of Cu species present in the catalyst, assuming the \( {\text{Cu}}^{ 2+ } \to {\text{Cu}}^{0} \) stoichiometry. The combination of experimental findings in this work lends support to a hypothesis that different TPR peaks are indicative of different types of sites rather than of step-wise reduction of copper species.

Construction and In Vitro/In Vivo Targeting of PSMA-Targeted Nanoscale Microbubbles in Prostate Cancer

Prostate-specific membrane antigen (PSMA) is a highly specific biological marker and treatment target for prostate cancer. So ultrasound molecular imaging using PSMA antibody-loaded targeted nanoscale microbubbles (MBs) may contribute to the early diagnosis of prostate cancer. PSMA monoclonal antibody-loaded targeted nanoscale MBs were prepared using biotin-avidin technology. Antibody binding was evaluated with immunofluorescence. Using MKN45 gastric cancer cells as controls, the targeting capability of the targeted MBs was observed in prostate cancer cells (LNCaP and C4-2) under optical microscope. Contrast enhancement was monitored by an ultrasound system in C4-2, LNCaP, and MKN45 transplanted tumors in nude mice. The arrival time, time to peak, peak intensity, and duration of contrast enhancement of targeted and blank nanoscale MBs were compared and analyzed. Targeted PSMA monoclonal antibody-loaded nanoscale MBs were successfully synthesized. These MBs were stable and could specifically bind to LNCaP and C4-2 cells in vitro but did not bind to MKN45 cells. There were significant differences in peak intensity and duration of contrast enhancement between targeted and blank nanoscale MBs in both transplanted prostate tumors (P < 0.05). Among the three types of transplanted tumors with targeted nanoscale MBs, the peak intensity was significantly higher in prostate tumors (LNCaP and C4-2) than in gastric tumors (MKN45) (P < 0.05). PSMA monoclonal antibody-loaded targeted nanoscale MBs can target and bind to prostate cancer cells specifically and allow for obvious contrast enhancement in vivo. Therefore, this study lays a foundation for early diagnosis and targeted therapy for prostate cancer.

Fluorescence self-quenching of tetraphenylporphyrin in liquid medium

Self-quenching of the fluorescence emission of tetraphenylporphyrin at high concentrations in toluene at the ambient temperature (300K) is discussed in detail based on steady state and time-resolved fluorescence measurements. The fluorescence self-quenching is mainly attributed to re-absorption effect and the Förster type resonance energy transfer process (homotransfer). The re-absorption effect is found to deform the fluorescence emission spectra significantly in energy positions as well as relative intensities of different peaks at high concentrations. Nearly ideal fluorescence emission spectra are observed at a concentration ∼10−7mol/L. Moreover, there is an apparent enhancement of the fluorescence lifetime value of tetraphenylporphyrin in toluene at high concentrations, especially on the blue side of the fluorescence emission spectra. To the best knowledge of the authors, this is the first detail report on the fluorescence self-quenching of porphyrins in liquid medium. This finding carries great importance in view of the widespread research on porphyrins in the fields of solar light harvesting, artificial photosynthesis, photodynamic therapy, etc.

Combined efficacy of biologically synthesized silver nanoparticles and different antibiotics against multidrug-resistant bacteria

Biological synthesis of nanoparticles is a growing innovative approach that is relatively cheaper and more environmentally friendly than current physicochemical processes. Among various microorganisms, fungi have been found to be comparatively more efficient in the synthesis of nanomaterials. In this research work, extracellular mycosynthesis of silver nanoparticles (AgNPs) was probed by reacting the precursor salt of silver nitrate (AgNO3) with culture filtrate of Aspergillus flavus. Initially, the mycosynthesis was regularly monitored by ultraviolet-visible spectroscopy, which showed AgNP peaks of around 400–470 nm. X-ray diffraction spectra revealed peaks of different intensities with respect to angle of diffractions (2θ) corresponding to varying configurations of AgNPs. Transmission electron micrographs further confirmed the formation of AgNPs in size ranging from 5–30 nm. Combined and individual antibacterial activities of the five conventional antibiotics and AgNPs were investigated against eight different multidrug-resistant bacterial species using the Kirby–Bauer disk-diffusion method. The decreasing order of antibacterial activity (zone of inhibition in mm) of antibiotics, AgNPs, and their conjugates against bacterial group (average) was; ciprofloxacin + AgNPs (23) . imipenem + AgNPs (21) > gentamycin + AgNPs (19) > vancomycin + AgNPs (16) > AgNPs (15) . imipenem (14) > trimethoprim + AgNPs (14) > ciprofloxacin (13) > gentamycin (11) > vancomycin (4) > trimethoprim (0). Overall, the synergistic effect of antibiotics and nanoparticles resulted in a 0.2–7.0 (average, 2.8) fold-area increase in antibacterial activity, which clearly revealed that nanoparticles can be effectively used in combination with antibiotics in order to improve their efficacy against various pathogenic microbes.

基于空间像峰值光强差的奇像差测量技术

基于空间像峰值光强差的奇像差测量技术

Measurement of phase fluctuations of Bose-Einstein condensates in an optical lattice

Even at zero temperature, there exist phase fluctuations associated with an array of Bose-Einstein condensates confined in a one-dimensional optical lattice. We demonstrate a method to measure the phase fluctuations based on the Fourier spectrum of the atomic density for a condensate released from the optical lattice. The phase variance is extracted from the relative intensities of different peaks in the Fourier spectrum. This method works even for high lattice depth where interference peaks disappear in the atomic density distribution.

Preparation of ultrafine tungsten wire via electrochemical method in an ionic liquid

Ultrafine tungsten wire less than 10μm in diameter is often used as wire array load applied in Inertial Confinement Fusion (ICF) physical experiments. In order to obtain a higher yield of X-ray, both initial radius and line quality of metal wire were required to be of high quality simultaneously. This paper has studied the electrochemical method to corrode tungsten wires uniformly in an ionic liquid electrolyte containing 1wt% sodium hydroxide. A three electrode system composed of a tungsten anode electrode, a stainless steel cathode and a saturated calomel electrode as a reference electrode, was used in the electrochemical experiments. Liner sweep voltammetry (LSV) and Tafel experiments were used to investigate the electrochemical behaviors of tungsten wires in ionic liquid and aqueous solution. Based on scanning electron microscope (SEM) observation, the morphologies of tungsten wire surface with uniform corrosion under different applied voltages have been demonstrated. X-ray diffraction (XRD) methods were employed to track the evolution of the crystal structure before and after corrosions, and there is an obvious difference in peak intensities. The ultrafine tungsten wire with a uniform diameter of 8.5μm was obtained under the optimized electric potential (2.5V) applied for decreasing diameter at 30°C.

Laser desorption VUV postionization MS imaging of a cocultured biofilm

Laser desorption postionization mass spectrometry (LDPI-MS) imaging is demonstrated with a 10.5 eV photon energy source for analysis and imaging of small endogenous molecules within intact biofilms. Biofilm consortia comprised of a synthetic Escherichia coli K12 coculture engineered for syntrophic metabolite exchange are grown on membranes and then used to test LDPI-MS analysis and imaging. Both E. coli strains displayed many similar peaks in LDPI-MS up to m/z 650, although some observed differences in peak intensities were consistent with the appearance of byproducts preferentially expressed by one strain. The relatively low mass resolution and accuracy of this specific LDPI-MS instrument prevented definitive assignment of species to peaks, but strategies are discussed to overcome this shortcoming. The results are also discussed in terms of desorption and ionization issues related to the use of 10.5 eV single-photon ionization, with control experiments providing additional mechanistic information. Finally, 10.5 eV LDPI-MS was able to collect ion images from intact, electrically insulating biofilms at ~100 μm spatial resolution. Spatial resolution of ~20 μm was possible, although a relatively long acquisition time resulted from the 10 Hz repetition rate of the single-photon ionization source.

Application of X-ray Photoelectron Spectroscopic Analysis to Protein Adsorption on Materials Relevant to Biomanufacturing

X-ray photoelectron spectroscopy (XPS) has been used to analyze the adsorption of a therapeutic monoclonal antibody (mAb), rituximab, and polyclonal human IgG (hIgG) on materials relevant to biomanufacturing of protein drug products. Details of the methods used to obtain qualitative confirmation of protein adsorption, using both the nitrogen (N 1s) signal originating from mAb proteins and an iodine heteroatom label, are presented. Both rituximab and hIgG were found to adsorb to a glass vial surface, vial rubber cap liner, syringe plunger tip, cell culture flask, serological pipette, and microcentrifuge tube. There was no evidence of protein adsorption on samples of polyvinylchloride (PVC) tubing or the barrel of a syringe. Differences in XPS heteroatom peak intensities, based on whether the heteroatom label was added to the protein prior to surface adsorption or after, suggest that adsorbed rituximab on a glass vial surface is in a structural conformation that allows extensive heteroatom labeling. Using a simple uniform overlayer model, the coverage of rituximab on a glass vial surface was determined by XPS to be 3.6 mg/m(2) , a value consistent with that expected for a theoretical monolayer.

Visual and Auditory Stimuli Associated with Swallowing Activate Mirror Neurons: A Magnetoencephalography Study

In the present study, we evaluated activated areas of the cerebral cortex with regard to the mirror neuron system during swallowing. To identify the activated areas, we used magnetoencephalography. Subjects were ten consenting volunteers. Swallowing-related stimuli comprised an animated image of the left profile of a person swallowing water with laryngeal elevation as a visual swallowing trigger stimulus and a swallowing sound as an auditory swallowing trigger stimulus. As control stimuli, a still frame image of the left profile without an additional trigger was shown, and an artificial sound as a false auditory trigger was provided. Triggers were presented at 3,000ms after the start of image presentation. The stimuli were combined and presented and the areas activated were identified for each stimulus. With animation and still-frame stimuli, the visual association area (Brodmann area (BA) 18) was activated at the start of image presentation, while with the swallowing sound and artificial sound stimuli, the auditory areas BA 41 and BA 42 were activated at the time of trigger presentation. However, with animation stimuli (animation stimulus, animation+swallowing sound stimuli, and animation+artificial sound stimuli), activation in BA 6 and BA 40, corresponding to mirror neurons, was observed between 620 and 720ms before the trigger. Besides, there were also significant differences in latency time and peak intensity between animation stimulus and animation+swallowing sound stimuli. Our results suggest that mirror neurons are activated by swallowing-related visual and auditory stimuli.

Poly(3-dodecylthienylenevinylene)s: Regioregularity and Crystallinity

A series of poly(dodecylthienylenevinylenes), C12-PTVs-a:b, with tunable regioregularity and solubility have been synthesized using two isomeric comonomers with molar ratios from 0:10 to 5:5, and characterized by NMR spectroscopy, differential scanning calorimetry, absorption spectroscopy, cyclovoltammetry, and X-ray diffraction. For the first time, the aromatic and olefinic 1H NMR peaks of regioregular head–tail Cn-PTVs are clearly assigned. No major difference in XRD peak intensity is observed among regiorandom and fully regioregular C12-PTVs. Voc of C12-PTVs-a:b and PC60BM blend solar cells are in the range of 0.43 to 0.51 V and consistently decrease as regioregularity is reduced. C12-PTV-3:7:PC60BM solar cells give the highest short-circuit current and practically same efficiency as that of C12-PTV-1:9:PC60BM devices. The results suggest a new strategy to enhance processability of optoelectronic polymers without sacrificing their crystallinity and device performance.

Analysis of Structural Variability in Pharmaceutical Excipients Using Solid-State NMR Spectroscopy

Polysaccharide-based excipients comprise the majority of most solid dosage forms and can vary dramatically in terms of structural and functionally related properties. Analytical methods for characterizing these important formulation components are crucial. Solid-state NMR spectroscopy (SSNMR) can provide a wealth of information on these materials while offering the advantages of non-destructive sample preparation and selectivity. The overall objective of this work is to identify SSNMR parameters that can be used to detect differences among these excipients. Excipients were obtained from a wide range of suppliers and analyzed as received; (13)C SSNMR spectra were acquired using a Chemagnetics CMX-300 spectrometer operating at approximately 75 MHz. The resolution of SSNMR signals of many excipients allows for positive identification of the major form present. Alginic acid and sodium alginate can be differentiated based on carbonyl peak position. Analysis of relative peak intensities provides insight into the purity of a carrageenan sample compared to known standards. The SSNMR spectrum of starch can be used to identify the source and to quantitate the amorphous and crystalline content. Relaxation values and peak areas of starch derivatives can be related to the degree of hydrolysis, providing an alternative method for determining dextrose equivalent. Differences in peak intensities and relaxation time values of HPMC samples can be correlated to the amount of methoxy subsituent groups. Important characteristics of excipients such as form identification, structural differences, crystalline and amorphous content, and water content variations can be detected using SSNMR spectroscopy.

The enhanced cortical activation induced by transcranial direct current stimulation during hand movements

The aim of this study is to evaluate whether tDCS applied on the primary motor cortex (M1) in company with hand movements could enhance cortical activation, using functional MRI (fMRI). Twelve right-handed normal subjects were recruited. Real tDCS and sham tDCS with hand movements were applied during fMRI scanning. Subjects performed grasp-release hand movements at a metronome-guided frequency of 1 Hz, while direct current with 1.0 mA was delivered to the primary motor cortex. The averaged cortical map and the intensity index were compared between real tDCS with hand movements and sham tDCS with hand movements. Our result showed that cortical activation on the primary sensorimotor cortex was observed under both of two conditions; real tDCS with hand movements and sham tDCS with hand movements. Voxel count and peak intensity were 365.10 ± 227.23 and 5.66 ± 1.97, respectively, in the left primary sensorimotor cortex during real tDCS with right hand movements; in contrast, those were 182.20 ± 117.88 and 4.12 ± 0.88, respectively, during sham tDCS with right hand movements. Significant differences in voxel count and peak intensity were observed between real tDCS and sham tDCS ( p < 0.05). We found that anodal tDCS application during motor task enhanced cortical activation on the underlying targeted motor cortex, compared with the same motor task without tDCS. Therefore, it seemed that tDCS induced more cortical activity and modulated brain function when concurrently applied with motor task.

MEASUREMENTS OF ISOTOPE EFFECTS IN THE PHOTOIONIZATION OF N 2 AND IMPLICATIONS FOR TITAN'S ATMOSPHERE

Isotope effects in the non-dissociative photoionization of molecular nitrogen (N_2 + hν → N_2^+ + e^−) may play a role in determining the relative abundances of isotopic species containing nitrogen in interstellar clouds and planetary atmospheres but have not been previously measured. Measurements of the photoionization efficiency spectra of ^(14)N^2, ^(15)N^(14)N, and ^(15)N_2 from 15.5 to 18.9 eV (65.6–80.0 nm) using the Advanced Light Source at Lawrence Berkeley National Laboratory show large differences in peak energies and intensities, with the ratio of the energy-dependent photoionization cross sections, σ(^(14)N_2)/σ (^(15)N^(14)N), ranging from 0.4 to 3.5. Convolving the cross sections with the solar flux and integrating over the energies measured, the ratios of photoionization rate coefficients are J(^(15)N^(14)N)/J(^(14)N_2) = 1.00 ± 0.02 and J(^(15)N_2)/J(^(14)N_2) = 1.00 ± 0.02, suggesting that isotopic fractionation between N_2 and N_2^+ should be small under such conditions. In contrast, in a one-dimensional model of Titan’s atmosphere, isotopic self-shielding of ^(14)N_2 leads to values of J(^(15)N^(14)N)/J(^(14)N_2) as large as ~1.17, larger than under optically thin conditions but still much smaller than values as high as ~29 predicted for N_2 photodissociation. Since modeled photodissociation isotope effects overpredict the HC^(15)N/HC^(14)N ratio in Titan’s atmosphere, and since both N atoms and N_2^+ ions may ultimately lead to the formation of HCN, estimates of the potential of including N_2 photoionization to contribute to a more quantitative explanation of ^(15)N/^(14)N for HCN in Titan’s atmosphere are explored.

Label-free peptide profiling of Orbitrap™ full mass spectra.

BackgroundWe developed a new version of the open source software package Peptrix that can yet compare large numbers of Orbitrap™ LC-MS data. The peptide profiling results for Peptrix on MS1 spectra were compared with those obtained from a small selection of open source and commercial software packages: msInspect, Sieve™ and Progenesis™. The properties compared in these packages were speed, total number of detected masses, redundancy of masses, reproducibility in numbers and CV of intensity, overlap of masses, and differences in peptide peak intensities. Reproducibility measurements were taken for the different MS1 software applications by measuring in triplicate a complex peptide mixture of immunoglobulin on the Orbitrap™ mass spectrometer. Values of peptide masses detected from the high intensity peaks of the MS1 spectra by peptide profiling were verified with values of the MS2 fragmented and sequenced masses that resulted in protein identifications with a significant score.FindingsPeptrix finds about the same number of peptide features as the other packages, but peptide masses are in some cases approximately 5 to 10 times less redundant present in the peptide profile matrix. The Peptrix profile matrix displays the largest overlap when comparing the number of masses in a pair between two software applications. The overlap of peptide masses between software packages of low intensity peaks in the spectra is remarkably low with about 50% of the detected masses in the individual packages. Peptrix does not differ from the other packages in detecting 96% of the masses that relate to highly abundant sequenced proteins. MS1 peak intensities vary between the applications in a non linear way as they are not processed using the same method.ConclusionsPeptrix is capable of peptide profiling using Orbitrap™ files and finding differential expressed peptides in body fluid and tissue samples. The number of peptide masses detected in Orbitrap™ files can be increased by using more MS1 peptide profiling applications, including Peptrix, since it appears from the comparison of Peptrix with the other applications that all software packages have likely a high false negative rate of low intensity peptide peaks (missing peptides).

Three-dimensional fluorescence spectral characterization of soil dissolved organic matters in the fluctuating water-level zone of Kai County, Three Gorges Reservoir

Three-dimensional fluorescence spectroscopy was used to investigate the fluorescent properties of soil dissolved organic matter (DOM) in the water-level-fluctuation zone (WLFZ) of Kai County, Three Gorges Reservoir (TGR). Most of the soil DOM analyzed in this study was found to contain four fluorescence peaks. Peaks A and C represent humic-like fluorescence, whereas peaks B and D represent tryptophan-like fluorescence. Peaks E and F, which represent tyrosine-like fluorescence, only appeared in certain soils. Soil humus was the main source of DOM in soil, and higher concentration of soil DOM was found in the exposed soil than submerged soil. Compared to the peaks A and B, the fluorescence intensities of peaks C and D were strongly influenced by the fluctuating water level. Analysis of fluorescence intensities of different peaks in soil DOM showed that WLFZ soil was not contaminated significantly. Soil DOM contained at least two types of humic-like fluorescence groups and two types of protein-like fluorescence groups. The proportion of the content of peak A in soil organic matter was quite stable. The soil DOM in exposed soil had relatively high humification and aromaticity, and periodic submerging and exposure of soil had an impact on the humification of soil DOM.

Comparison between relay propagation and direct propagation of Gaussian-Schell-model beam in turbulent atmosphere along a slant path

The relay propagation of Gaussian–Schell-model in turbulent atmosphere along a slant path is studied in this paper. Based on the extended Huygens–Fresnel principle and a quadratic approximation, an analytical formula of average intensity for Gaussian–Schell-model beams in turbulent atmosphere along a slant path is derived, and some special cases are discussed. From the study and the comparison with the direct propagation, we can see that the relay propagation has an advantage over the direct propagation. When the altitude of the target is low, the peak intensity of relay propagation is much larger than that of direct propagation. However, because of the limitation of the relay system aperture for relay propagation and the variation of coherence length for direct propagation, the difference in peak intensity between the two propagations decreases with the increase of the target altitude.

Assessing the Quality and Reproducibility of a Proteomic Platform for Clinical Stroke Biomarker Discovery

The aim of this study was to investigate the quality and reproducibility of mass spectra derived from a matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) platform in a patient population undergoing carotid endarterectomy. Plasma samples were either digested with trypsin or left undigested, fractionated with either C18 or weak cation exchange (WCX) columns and analysed by MALDI-TOF MS. Quality of mass spectra for each method was assessed by baseline correction (lower area under the curve ratio indicating higher quality) and signal-to-noise ratio. Mean coefficient of variation (CV%) assessed reproducibility between repeated experiments and methods. Identified mass peak intensity differences were assessed for consistency across repeated experiments. Plasma from six patients was analysed. The quality of mass spectra was significantly better when derived from digested plasma fractionated by either WCX or C18 methods compared to undigested plasma fractionated by WCX (analysis of variance, p < 0.05). Mean CV% for repeated experiments was 18% and 28% for WCX and C18 fractionated digested plasma, respectively. A small number of differences in mass peak intensities were consistently observed in repeated experiments. Repeated experiments are required to confidently identify non-random mass peak intensity differences as putative plasma biomarkers that merit further investigation.