•Laser spectroscopic characterization of single extraterrestrial dust particles using optical trapping-cavity ringdown and Raman spectroscopy.•Single-particle extinctions of single trapped ...extraterrestrial dust particles were measured using cavity ringdown spectroscopy.•Raman spectral features of chemical groups in individually trapped particles were characterized.•Demonstrated optical trapping cavity ringdown spectroscopy and optical trapping Raman spectroscopy techniques for extraterrestrial dust particles.
Earth's atmosphere contains interplanetary dust particles (IDPs), which are a key ingredient to understand planetary phenomena, yet the study of their physicochemical properties without external interferences at the single-particle level is limited. With the optical-trapping (OT) technique, a single dust particle can be stably trapped in air for subsequent characterization. We report on measurements of the single-particle extinction of trapped particles using cavity ringdown spectroscopy at ultraviolet wavelength around 308 nm. We also present Raman spectral features of chemical groups in individually trapped particles. Two simulants of extraterrestrial materials, (Martian and lunar analogs) along with carbon spheres and volcanic ashes were trapped and spectroscopically characterized. In addition to the on-trap measurements, the particles’ morphological and mineralogical information was obtained from off-trap measurements using scanning electron microscopy and energy dispersive spectroscopy. This study demonstrates that the integration of OT with cavity ringdown and Raman spectroscopy provides a new tool to gain multimodal information on the physicochemical properties of single IDPs with minimum to no external interferences.
A new method is demonstrated for optically trapping micron-sized absorbing particles in air and obtaining their single-particle Raman spectra. A 488-nm Gaussian beam from an Argon ion laser is ...transformed by conical lenses (axicons) and other optics into two counter-propagating hollow beams, which are then focused tightly to form hollow conical beams near the trapping region. The combination of the two coaxial conical beams, with focal points shifted relative to each other along the axis of the beams, generates a low-light-intensity biconical region totally enclosed by the high-intensity light at the surface of the bicone, which is a type of bottle beam. Particles within this region are trapped by the photophoretic forces that push particles toward the low-intensity center of this region. Raman spectra from individual trapped particles made from carbon nanotubes are measured. This trapping technique could lead to the development of an on-line real-time single-particle Raman spectrometer for characterization of absorbing aerosol particles.
Carbon nanotubes (CNTs) have become recognized as a potential environmental and health hazard as their applications are broadening and manufacturing costs are reducing. Fundamental information of ...CNTs in air is of significant importance to our understanding of their environmental fate as well as to further applications. Extensive efforts have been made over decades on characterizing CNTs; however, a majority of the studies are of bulk or CNTs dispersed on substrates. In the present study, we characterize single CNT particles in air using optical trapping Raman spectroscopy (OT-RS). Different types of CNT particles, as well as glassy carbon spheres, were optically trapped in air. Their physical properties were viewed by microscopic bright field images and scattering images; their chemical properties and structural information can be inferred from characteristic Raman bands. The system can also spatially resolve the morphology and chemical distribution of optically trapped CNT particles in air. The OT-RS technique combines single-particle morphological and chemical information and offers an online method to characterize the physicochemical properties of single CNT particles at their native states in air.
We demonstrate photophoretic trapping of micron-sized absorbing particles in air using pulsed and continuous-wave (CW) ultraviolet laser illumination at wavelengths of 351 nm and 244 nm. We compared ...the particle trapping dynamics in two trapping geometries consisting of a hollow optical cone formed by light propagating either with or against gravity. This comparison allowed us to isolate the influence of the photophoretic force from the radiative pressure and the convective forces. We found that the absorbing spherical particles tested experienced a positive photophoretic force, whereas the spatially irregular, non-spherical particles tested experienced a negative photophoretic force. By using two trapping geometries, both spherical and non-spherical absorbing particles could be trapped and held securely in place. The position of the trapped particles exhibited a standard deviation of less than 1 µm over 20 seconds. Moreover, by operating in the UV and deep-UV where the majority of airborne materials are absorptive, the system was able to trap a wide range of particle types. Such a general purpose optical trap could enable on-line characterization of airborne particles when coupled with interrogation techniques such as Raman spectroscopy.
Colon cancer (CC), one of the most common malignancies worldwide, lacks an effective prognostic prediction biomarker. N7-methylguanosine (m7G) methylation is a common RNA modification type and has ...been proven to influence tumorigenesis. However, the correlation between m7G-related genes and CC remains unclear. The gene expression levels and clinical information of CC patients were downloaded from public databases. Twenty-nine m7G-related genes were obtained from the published literature. Via unsupervised clustering based on the expression levels of m7G-related genes, CC patients were divided into three m7G clusters. Based on differentially expressed genes (DEGs) from the above three groups, CC patients were further divided into three gene clusters. The m7G score, a prognostic model, was established using principal component analysis (PCA) based on 15 prognosis-associated m7G genes. KM curve analysis demonstrated that the overall survival rate was remarkably higher in the high-m7G score group, which was much more significant in advanced CC patients as confirmed by subgroup analysis. Correlation analysis indicated that the m7G score was associated with tumor mutational burden (TMB), PD-L1 expression, immune infiltration, and drug sensitivity. The expression level of prognosis-related m7G genes was further confirmed in human CC cell lines and samples. This study established an m7G gene-based prognostic model (m7G score), which demonstrated the important roles of m7G-related genes during CC initiation and progression. The m7G score could be a practical biomarker to predict immunotherapy response and prognosis in CC patients.
We present an advanced optical method to measure the phase function of circular intensity differential scattering (CIDS), i.e., the normalized Mueller matrix element -S
14
/S
11
, from individual ...single flowing through aerosol particles. Here, a 32-anode photomultiplier tube and its associated electronics, combined with an elliptical reflector, were used to record the scattering phase functions, when a particle were illuminated by a left-handed and a right-handed circular polarization laser beam around the focus of the reflector successively. The new design does not need lock-in amplifier, polarization modulator, and rotating goniometer as the traditional setup. It can reach a particle detection ability with a maximum rate of 50,000 particle/sec. CIDS phase functions from tryptophan particles, polystyrene latex microspheres, aggregates of Escherichia coli, Bacillus subtilis spores, Yersinia rohdei, and bacteriophage MS2 were measured, the results showed that this method has the ability to rapidly discriminate between single bioaerosol and non-bioaerosol particles.
Determination of the mechanisms of interspecies transmission is of great significance for the prevention of epidemic diseases caused by emerging coronaviruses (CoVs). Recently, porcine ...deltacoronavirus (PDCoV) was shown to exhibit broad host cell range mediated by surface expression of aminopeptidase N (APN), and humans have been reported to be at risk of PDCoV infection. In the present study, we first demonstrated overexpression of APN orthologues from various species, including mice and felines, in the APN-deficient swine small intestine epithelial cells permitted PDCoV infection, confirming that APN broadly facilitates PDCoV cellular entry and perhaps subsequent interspecies transmission. PDCoV was able to limitedly infect mice
, distributing mainly in enteric and lymphoid tissues, suggesting that mice may serve as a susceptible reservoir of PDCoV. Furthermore, elements (two glycosylation sites and four aromatic amino acids) on the surface of domain B (S1
) of the PDCoV spike glycoprotein S1 subunit were identified to be critical for cellular surface binding of APN orthologues. However, both domain A (S1
) and domain B (S1
) were able to elicit potent neutralizing antibodies against PDCoV infection. The antibodies against S1
inhibited the hemagglutination activity of PDCoV using erythrocytes from various species, which might account for the neutralizing capacity of S1
antibodies partially through a blockage of sialic acid binding. The study reveals the tremendous potential of PDCoV for interspecies transmission and the role of two major PDCoV S1 domains in receptor binding and neutralization, providing a theoretical basis for development of intervention strategies.
Coronaviruses exhibit a tendency for recombination and mutation, which enables them to quickly adapt to various novel hosts. Previously, orthologues of aminopeptidase N (APN) from mammalian and avian species were found to be associated with porcine deltacoronavirus (PDCoV) cellular entry
. Here, we provide
evidence that mice are susceptible to PDCoV limited infection. We also show that two major domains (S1
and S1
) of the PDCoV spike glycoprotein involved in APN receptor binding can elicit neutralizing antibodies, identifying two glycosylation sites and four aromatic amino acids on the surface of the S1
domain critical for APN binding and demonstrating that the neutralization activity of S1
antibodies is partially attributed to blockage of sugar binding activity. Our findings further implicate PDCoV's great potential for interspecies transmission, and the data of receptor binding and neutralization may provide a basis for development of future intervention strategies.
The circular intensity differential scattering (CIDS), i.e. the normalized Mueller matrix element -S
/S
, can be used to detect the helical structures of DNA molecules in biological systems, however, ...no CIDS measurement from single particles has been reported to date. We report an innovative method for measuring CIDS phase functions from single particles individually flowing through a scattering laser beam. CIDS signals were obtained from polystyrene latex (PSL) microspheres with or without coating of DNA molecules, tryptophan particles, and aggregates of B. subtilis spores, at the size of 3 μm in diameter. Preliminary results show that this method is able to measure CIDS phase function in tens of microseconds from single particles, and has the ability to identify particles containing biological molecules.
•Elastic light scattering (ELS) of aerosol particles.•Detection and characterization of single aerosol particles.•Bioaerosol detection using elastic light scattering.•Discriminating bioaerosol from ...atmospheric aerosols.
Elastic light scattering (ELS) from single micron-sized particles has been used as a fast, non-destructive diagnostic tool in life science, physics, chemistry, climatology, and astrophysics. Due to the large scattering cross-section, ELS can be used to find trace amounts of suspect particles such as bioaerosols among complex, diverse atmospheric aerosols, based on single-particle interrogation. In this article, we briefly summarized the main computational models and instrumentation developed for ELS, then reviewed how properties like particle size, refractive index, degree of symmetry, and surface roughness, in addition to packing density, shape of primary particles in an aggregate, and special helix structures in compositions can be determined from ELS measurements. Meanwhile, we emphasize on how these parameters obtained from ELS measurements can be used for bioaerosol detection, characterization, and discrimination from atmospheric aerosol particles using different classification algorithms.
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