芭蕉根拉曼光谱鉴别研究

目的为芭蕉根的进一步研究开发提供鉴别依据。方法采用拉曼光谱鉴别芭蕉根及其易混淆品。结果芭蕉根及其易混淆品在拉曼光谱图中均有各自的特征峰,可容易地将它们区别开。结论拉曼光谱特征可作为芭蕉根的生药鉴别依据。     

Microstructural Characterisation and Wear Behaviour of Diamond Composite Materials

Since the initial research leading to the production of diamond composite materials, there have been several important developments leading to significant improvements in the properties of these superhard composite materials. Apart from the fact that diamonds, whether originating from natural resources or synthesised commercially, are the hardest and most wear-resistant materials commonly available, there are other mechanical properties that limit their industrial application. These include the low fracture toughness and low impact strength of diamond. By incorporating a range of binder phases into the sintering production process of these composites, these critically important properties have been radically improved. These new composites can withstand much higher operating temperatures without markedly reducing their strength and wear resistance. Further innovative steps are now being made to improve the properties of diamond composites by reducing grain and particle sizes into the nano range. This review will cover recent developments in diamond composite materials with special emphasis on microstructural characterisation. The results of such studies should assist in the design of new, innovative diamond tools as well as leading to radical improvements in the productivity of cutting, drilling and sawing operations in the exploration, mining, civil construction and manufacturing industries.     

Strain-induced crack formations in PDMS/DXA drug collars

Drug-eluting systems are currently used in cardiac leads in order to reduce inflammation and fibrosis at the lead–tissue interface. Drug release from these drug delivery systems can be modulated by the manufacturing processes used to create the drug systems and assemble them onto the cardiac lead. In this study, scanning electron microscopy, atomic force microscopy and Raman microscopy are employed to explore the material characteristics of a polydimethylsiloxane–dexamethasone acetate drug collar used on cardiac leads when varying the strain during collar assembly on the lead. A novel test fixture was created in order to investigate these drug collars under simulated stresses. Measurements of the collar while fitted to a rod revealed microcracks that are hypothesized to affect the drug release performance, resulting in increased drug elution. It was found that the strain that occurs during assembly of the collar onto the lead is a key factor in the formation of these microcracks. Results also suggest that cracks tend to form in areas of high drug particle density, and propagate between drug particles.     

Electrocatalytic reduction of hydrogen peroxide at Prussian blue modified electrode: An in situ Raman spectroelectrochemical study

Electrodeposited layers of Prussian blue (PB) and electrocatalytic reduction of hydrogen peroxide at electrodes, modified with these layers have been studied with in situ Raman spectroelectrochemical technique. Characteristic Raman features have been observed and attributed to reversible electrochemical transition between the oxidized (PB) and reduced (Prussian white, PW) forms of the modifier. It has been shown that, during the cathodic reduction of hydrogen peroxide, PW layer turns partially into its oxidized form PB even at electrode potentials corresponding to the reduced form of a modifier. The ratio of PB/PW within the modifier layer has been shown to depend on peroxide concentration, indicating that electrocatalysis proceeds within the modifier layer rather than at an outer modifier/electrolyte interface. As opposite, electrooxidation of ascorbate does not affect in situ Raman spectra and thus proceeds most probably at an outer interface. The kinetics of PB decomposition during electrocatalytic reduction of hydrogen peroxide has been studied by in situ Raman spectroscopy, and the corresponding first-order reaction rate constant has been obtained.     

Vibrational imaging of newly synthesized proteins in live cells by stimulated Raman scattering microscopy

Synthesis of new proteins, a key step in the central dogma of molecular biology, has been a major biological process by which cells respond rapidly to environmental cues in both physiological and pathological conditions. However, the selective visualization of a newly synthesized proteome in living systems with subcellular resolution has proven to be rather challenging, despite the extensive efforts along the lines of fluorescence staining, autoradiography, and mass spectrometry. Herein, we report an imaging technique to visualize nascent proteins by harnessing the emerging stimulated Raman scattering (SRS) microscopy coupled with metabolic incorporation of deuterium-labeled amino acids. As a first demonstration, we imaged newly synthesized proteins in live mammalian cells with high spatial–temporal resolution without fixation or staining. Subcellular compartments with fast protein turnover in HeLa and HEK293T cells, and newly grown neurites in differentiating neuron-like N2A cells, are clearly identified via this imaging technique. Technically, incorporation of deuterium-labeled amino acids is minimally perturbative to live cells, whereas SRS imaging of exogenous carbon–deuterium bonds (C–D) in the cell-silent Raman region is highly sensitive, specific, and compatible with living systems. Moreover, coupled with label-free SRS imaging of the total proteome, our method can readily generate spatial maps of the quantitative ratio between new and total proteomes. Thus, this technique of nonlinear vibrational imaging of stable isotope incorporation will be a valuable tool to advance our understanding of the complex spatial and temporal dynamics of newly synthesized proteome in vivo.     

Near‐infrared Raman spectroscopy for optical diagnosis in the stomach: Identification of Helicobacter‐pylori infection and intestinal metaplasia

Raman spectroscopy is a unique vibrational spectroscopic technique which can be used to probe biochemicals and biomolecular structures and conformations of tissues. The main objective of this study is to evaluate the feasibility of applying near‐infrared (NIR) Raman spectroscopy for identification of nonneoplastic lesions (Helicobacter‐pylori (Hp) infection, and intestinal metaplasia (IM)) highly associated with stomach cancer. A rapid‐acquisition NIR Raman spectroscopic system was used for tissue Raman measurements at 785 nm excitation, and a total of 88 gastric tissue samples (57 normal; 11 Hp‐infection; 20 IM) from 56 patients were measured. The principal components analysis (PCA) and linear discriminant analysis (LDA) techniques were implemented to develop effective diagnostic algorithms for classification of Raman spectra of different gastric tissue types. High‐quality Raman spectra in the range of 800‐1800 cm⁻¹ were acquired from gastric tissue within 5 seconds. Significant spectral differences in Raman spectra were observed among normal, Hp‐infection and IM gastric tissue, particularly in the spectral ranges of 848–917, 960–1015, 1088–1133, 1206–1213, 1277–1313, 1395–1445, 1517–1549, 1607–1690, and 1714–1767 cm⁻¹ which contained signals related to proteins, lipids and porphyrin. PCA‐LDA algorithms developed together with leave one patient out, cross validation technique yield diagnostic sensitivities of 91.7%, 80.0%, and 80.0%, and specificities of 80.0%, 100%, and 92.7%, respectively, for classification of normal, Hp‐infection and IM gastric tissues. This work demonstrates the utility of NIR Raman spectroscopy for early diagnosis of Hp‐infection and IM lesions in the gastric at the molecular level.     

Use of Raman spectroscopy for the early detection of filaggrin‐related atopic dermatitis

Background: Filaggrin (FLG) gene mutations, which result in complete or incomplete loss of proFLG/FLG peptides, have been reported as an important predisposing factor for atopic dermatitis (AD) and secondary atopic phenotypes such as atopic asthma. Method: The presence of the protein FLG in the skin was evaluated at birth on 12 infants using Raman spectroscopy; these 12 infants were monitored for 1 year to see whether they developed AD. Three different statistical analysis procedures, two of which involved principal component analysis (PCA), were performed on the Raman spectra in order to determine the FLG content. Results: The infants who had a lower FLG content, determined using any of the three statistical analysis procedures proposed, were also the ones that clinically developed AD. Conclusion: The results suggest that Raman spectroscopy and statistical analysis such as PCA could be used as an early detection procedure for FLG ‐related AD and as a possible quantitative marker for FLG gene mutations.     

Early cortical lens opacities: a short overview

Cataract is still the dominant cause of blindness worldwide. Cortical cataract is the most prevalent of the age‐related changes in the human lenses that require surgical intervention to restore vision. The absence of adequate cataract surgery in most developing countries is the main cause of the high prevalence of cataract blindness worldwide. Lens ageing is accompanied by dramatic increases in stiffness, light scattering and coloration of the lens nucleus. These changes start to become manifest as early as the fourth or fifth decade of life and lead to nuclear cataract in old age. In the same period the equatorial deep lens cortex starts to show small opaque shades, which eventually grow out to segmental and annular opacities. These opaque shades are filled with small vesicles and contain abnormal amounts of cross‐linked proteins, cholesterol and phospholipids. They are bordered by membranes that are rich in square arrays, have ‘degenerate’ gap junctions and have few intramembranous particles. It has been shown that the opaque shades represent cohorts of locally affected fibres segregated from unaffected neighbouring fibres by ‘non‐leaky’ membranes. This segregation is an effective mechanism delaying the outgrowth of these opacities to cuneiform cataracts entering the pupillary space and thus leading to blinding cortical cataracts. Although cataract formation is mostly considered to be a multi‐factorial disease, oxidative stress might be one of the leading causes for both nuclear and cortical cataract. In cortical cataracts shear stress between cortex and nucleus during accommodation may also play a significant role.