Differentiation of body fluid stains on fabrics using external reflection Fourier transform infrared spectroscopy (FTIR) and chemometrics

Body fluids are evidence of great forensic interest due to the DNA extracted from them, which allows genetic identification of people. This study focuses on the discrimination among semen, vaginal fluid and urine stains (main fluids in sexual crimes) placed on different coloured cotton fabrics by external reflection FTIR spectroscopy combined with chemometrics. Semen-vaginal fluid mixtures and potential false positive substances commonly found in daily life such as soaps, milk, juices and lotions were also studied. Results demonstrated that the IR spectral signature obtained for each body fluid allowed its identification and the correct classification of unknown stains by means of Principal Components Analysis (PCA) and Soft Independent Modelling of Class Analogy (SIMCA). Interestingly, results proved that these IR spectra did not show any bands due to the colour of the fabric and no substance of those present in daily life which were analysed, provided a false positive

Biophysical studies in polymer therapeutics: the interactions of anionic and cationic PAMAM dendrimers with lipid monolayers

Understanding how polymers interact with biological membranes is important for the development of polymer based therapeutics and wider biomedical applications. Here, biophysical methods (surface pressure measurements, external reflection FTIR) have been used to investigate the interaction between PAMAM dendrimers (Generation 5 or 4.5) and anionic (DPPG) or zwitterionic (DPPC) model membranes. We observed a concentration-dependent binding behaviour of both PAMAM species to both model membranes; however, equivalent levels of penetration into DPPC monolayers required approximately 10-fold higher dendrimer concentrations than for penetration into DPPG monolayers. Overall, the anionic PAMAM G4.5 showed a slightly better penetration ability which could be caused by repulsive forces towards the lipid layers. In comparison, increasing concentration of cationic PAMAM G5 leads to saturation of adsorption at the anionic lipid surface before penetration into the lipid layer likely driven by electrostatic attraction. Our studies also showed that physiologically relevant concentrations of sodium chloride (144 mM) decreased PAMAM penetration into DPPG monolayers but did not significantly affect the dendrimer-DPPC interaction. These results provide an insight into the mechanism of interaction between charged dendritic polymers with a lipid interface and show that the nature of such interactions are affected by lipid headgroup, dendrimer charge and solution salinity

Selected wheat seed defense proteins exhibit competitive binding to model microbial lipid interfaces

Puroindolines (Pins) and purothionins (Pths) are basic, amphiphilic, cysteine-rich wheat proteins that play a role in plant defense against microbial pathogens. We have examined the co-adsorption and sequential addition of Pins (Pin-a, Pin-b and a mutant form of Pin-b with Trp-44 to Arg-44 substitution) and β-purothionin (β-Pth) model anionic lipid layers, using a combination of surface pressure measurements, external reflection FTIR spectroscopy and neutron reflectometry. Results highlighted differences in the protein binding mechanisms, and in the competitive binding and penetration of lipid layers between respective Pins and β-Pth. Pin-a formed a blanket-like layer of protein below the lipid surface that resulted in the reduction or inhibition of β-Pth penetration of the lipid layer. Wild-type Pin-b participated in co-operative binding with β-Pth, whereas the mutant Pin-b did not bind to the lipid layer in the presence of β-Pth. The results provide further insight into the role of hydrophobic and cationic amino acid residues in antimicrobial activity

Thiocarbonate collectors in pyrite flotation ? fundamentals and applications

Journal ArticleRecent results from electrochemical measurements demonstrate that trithiocarbonate (TTC) collectors are more readily oxidized to their corresponding dithiolates than the dithiocarbonate/xanthate (DTC) collectors. Based on the traditional analysis of collector adsorption, trithiocarbonates might then be expected to be effective for bulk sulfide mineral flotation. Previous bench-scale flotation research had shown that TTC collectors are very effective for the flotation of copper sulfide minerals and PGM (platinum group metal) sulfide minerals

Historical silk: a novel method to evaluate degumming with non-invasive infrared spectroscopy and spectral deconvolution

: To correctly manage a collection of historical silks, it is important to detect if the yarn has been originally subjected to degumming. This process is generally applied to eliminate sericin; the obtained fiber is named soft silk, in contrast with hard silk which is unprocessed. The distinction between hard and soft silk gives both historical information and useful indications for informed conservation. With this aim, 32 samples of silk textiles from traditional Japanese samurai armors (15th-20th century) were characterized in a non-invasive way. ATR-FTIR spectroscopy has been previously used to detect hard silk, but data interpretation is challenging. To overcome this difficulty, an innovative analytical protocol based on external reflection FTIR (ER-FTIR) spectroscopy was employed, coupled with spectral deconvolution and multivariate data analysis. The ER-FTIR technique is rapid, portable, and widely employed in the cultural heritage field, but rarely applied to the study of textiles. The ER-FTIR band assignment for silk was discussed for the first time. Then, the evaluation of the OH stretching signals allowed for a reliable distinction between hard and soft silk. Such an innovative point of view, which exploits a "weakness" of FTIR spectroscopy-the strong absorption from water molecules-to indirectly obtain the results, can have industrial applications too

Effect of CTAB Ratio to the Characters of Mesoporous Silica Prepared from Rice Husk Ash in the Pyrolysis of a–cellulose

Due to its wide application, synthesizing silica through a cost-effective process becomes an attractive subject to be studied today. In this work, mesoporous silica (MS) was prepared from the highly available agricultural waste, rice husk ash (RHA), to be used as catalyst in the pyrolysis of a-cellulose. Silica was extracted from RHA through a reflux process in a strong base solution and arranged into a mesoporous structure by using cetyltrimethylammonium bromide (CTAB). To find a condition that produces a mesoporous support with the highest surface area and catalytic activity, the mole ratios of CTAB:SiO2 used during the preparation of MS were varied; 0.05:1; 0.1:1; 0.2:1. Afterwards, all prepared MS were characterized using Fourier Transform Infra Red (FTIR), Scanning Electron Microscope (SEM), and Surface Area Analyzer (SAA). Through he surface area analysis, it was found that MS materials possessed surface area, pore diameter, and pore volume that range from 600–970 m2.g−1, 3.5–4.7 nm, 0.7–1 cm3.g−1, respectively. The highest surface area, with over 970.80 m2.g−1, was obtained in MS support prepared by using CTAB:SiO2 mole ratio of 0.1:1. SEM images showed a coral reef-like surface morphology for all MS. In the pyrolysis of a-cellulose evaluated by Py-GCMS, aside from producing biofuel compounds, the use of MS was able to generate two-fold furan production, which is considered as a valuable compound in many chemical syntheses. This result highlights the potential of MS prepared from RHA to be used as a catalysis support material that is more economical for biofuel and other chemical production. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

X-rays investigations for the characterization of two 17th century brass instruments from Nuremberg

A recent finding at the Castello Sforzesco in Milan of two brass natural horns from the end of the 17th century and assigned to the Haas family from Nuremberg brought to light new information about this class of objects. The instruments were heavily damaged, but their historical value was great. In this study, a multidisciplinary approach mainly based on non-invasive analytical techniques and including X-rays investigations (X-ray radiography, X-ray fluorescence and X-ray diffraction) was used. The present study was aimed at: i) pointing out the executive techniques for archaeometric purposes; ii) characterizing the morphological and the chemical features of materials; and iii) identifying and mapping the damages of the structure and the alterations of the surface

The role of lipid composition on the interaction between a tryptophan-rich protein and model bacterial membranes

The interaction between tryptophan-rich puroindoline proteins and model bacterial membranes at the air-liquid interface has been investigated by FTIR spectroscopy, surface pressure measurements and Brewster angle microscopy. The role of different lipid constituents on the interactions between lipid membrane and protein was studied using wild type (Pin-b) and mutant (Trp44 to Arg44 mutant, Pin-bs) puroindoline proteins. The results show differences in the lipid selectivity of the two proteins in terms of preferential binding to specific lipid head groups in mixed lipid systems. Pin-b wild type was able to penetrate mixed layers of phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) head groups more deeply compared to the mutant Pin-bs. Increasing saturation of the lipid tails increased penetration and adsorption of Pin-b wild type, but again the response of the mutant form differed. The results provide insight as to the role of membrane architecture, lipid composition and fluidity, on antimicrobial activity of proteins. Data show distinct differences in the lipid binding behavior of Pin-b as a result of a single residue mutation, highlighting the importance of hydrophobic and charged amino acids in antimicrobial protein and peptide activity

Surfactant Adsorption Kinetics by Total Internal Reflection Raman Spectroscopy. 2. CTAB and Triton X-100 Mixtures on Silica

Total internal reflection (TIR) Raman spectroscopy has been used to study the kinetics of adsorption, desorption, and displacement of mixed surfactant systems at the silica–water interface. The limited penetration depth of the evanescent wave provides surface sensitivity while the chemical sensitivity of Raman scattering permits the determination of the time-dependent composition of the adsorbed film. Principal component analysis is used to deconvolute the Raman spectra with a time resolution of 2 s and a precision of 5% of a monolayer. Both equilibrium and kinetic measurements are presented for the cetyltrimethylammonium bromide (CTAB)/Triton X-100 system over a range of concentrations and compositions. For a total concentration of 2 mM, the adsorption isotherm shows strong synergistic behavior with the addition of small amounts of CTAB (2% of the total surfactant) doubling the adsorbed amount of Triton X-100. This synergism has a marked influence on the kinetics: for example, when Triton X-100 replaces CTAB, the Triton X-100 surface excess overshoots its equilibrium value and returns only very slowly to equilibrium. For systems above the cmc, the repartitioning of surfactant between micelles and monomers results in unexpected behavior during exchange or rinsing of mixed surfactant solutions. For example, during rinsing, the more rapid diffusion of CTAB away from the surface leads to a local increase in the monomer concentration of Triton X-100, resulting in a temporary spike in the Triton X-100 surface excess. Displacement kinetics of CTAB by TX-100 and vice versa are generally slower than the adsorption or desorption of the pure surfactants but cover a wide range of kinetic time scales, depending on the details of the compositions and concentrations of the initial and final solutions

Surface Freezing in Surfactant/Alkane/Water Systems

Surface freezing transitions in mixed monolayers of a homologous series of cationic surfactants, the alkyltrimethyl ammonium bromides (CnTAB where n = 12, 14, 16, 18), as well as a range of non-ionic, zwitterionic and biological surfactants, have been investigated ellipsometrically with a range of n-alkanes (Cm where m = 12 – 20, 28). Two distinct solid phases are observed depending upon the chain length difference between surfactant and n-alkane. Type I solid phases consist of a surface frozen mixed monolayer and are formed when this difference is small. Type II solid phases are bilayer structures with a frozen layer of neat n-alkane above a liquid-like mixed monolayer. Type II freezing was thought to occur via wetting of surface frozen n-alkane, as previously reported type II transitions took place in the presence of surface frozen n-alkanes. Thermodynamically stable type II solid phases have now been found in the presence of n-alkanes that do not show surface freezing at the air/alkane interface, however, and so this picture is incomplete. In the presence of pentadecane, for example, the biological surfactant lyso-OPC forms a stable type II solid phase 6.5 °C above the n-alkane bulk melting point. Such a large surface freezing range is unprecedented for a type II system. Studies using external reflection FTIR (ER-FTIRS) and vibrational sum-frequency spectroscopies (VSFS) have been used to probe these novel behaviours. Results were fully consistent with the proposed structures of both type I and type II surface frozen layers. 2D correlation analysis of ER-FTIR spectra as a function of temperature showed that type II frozen layer formation does not proceed via a simple wetting transition, with the formation of a transient intermediate implied. Evidence for such an intermediate was provided by dynamic ellipsometry measurements on the type II C18TAB/n-eicosane system