Infrared and Raman Spectroscopic Studies of the Antimicrobial Effects of Garlic Concentrates and Diallyl Constituents on Foodborne Pathogens

Abstract

The antimicrobial effects of garlic (Allium sativum) extract (25, 50, 75, 100, and 200 μl/ml) and diallyl sulfide (5, 10 and 20 μM) on Listeria monocytogenes and Escherichia coli O157:H7 cultivated in tryptic soy broth at 4, 22 and 35°C for up to 7 days were investigated. L. monocytogenes was more resistant to garlic extract and diallyl compounds treatment than E. coli O157:H7. Fourier transform Infrared (FT-IR) spectroscopy indicated that diallyl constituents contributed more to the antimicrobial effect than phenolic compounds. This effect was verified by Raman spectroscopy and Raman mapping on single bacteria. Scanning electron microscope (SEM) and transmission electron microscope (TEM) showed cell membrane damage consistent with spectroscopic observation. The degree of bacterial cell injury could be quantified using chemometric methods.

Detection of Receptor-Induced Glycoprotein Conformational Changes on Enveloped Virions by Using Confocal Micro-Raman Spectroscopy

“…Spectral reproducibility was determined by calculating the differentiation index (D y1y2 ) value, as described in our previous studies (19,37 (19). Furthermore, spectra of both fresh NiV samples and frozen and then thawed NiV samples were collected (data not shown), and spectral reproducibility was suitable (D y1y2 value of Ͻ300).…”

“…However, these techniques require complicated and/or time-consuming methods for sample preparation and relatively large numbers of virions for identification. Raman spectroscopy is widely used for protein characterization, characterizing analytes by compiling vibrational properties of a wide range of functional groups together and providing information about chemical constituents of biological samples (19). Raman spectroscopy has also been employed to investigate nonviral protein structural variations (20).…”

“…In the current study, we employed Raman spectroscopy, principal component (PC) analysis (PCA), and chemometric methods to successfully discriminate glycoproteins (i.e., F and G) on the membrane of NiV VLPs or NiV/VSV pseudotyped virions (19,37). In addition, dynamic receptor-or temperature-induced conformational changes of these glycoproteins on NiV pseudovirions were monitored in situ by using a Raman spectroscopy-based twodimensional (2D) correlation synchronous plotting method.…”

Determining Ovarian Maturity in Farmed Sturgeon 1 (Acipenser transmontanus) for Caviar Production Using Fourier Transform Infrared Spectroscopy (FT-IR)

“…The first three PCs can explain over 80% of segregation capability of either the cluster or dendrogram models (Figures 2 and 3) with the most significant features being associated with changes to protein secondary structure: amide I (1695 cm -1 ) [7,20,21]; α-helical structures (1655 cm ) [19]; CO stretching of the C-OH groups of serine, threonine and tyrosine in the cell proteins (1172/1173 cm -1 ) [19]. For carbohydrate, the band at 1430 cm -1 is assigned to δ (CH2) of polysaccharide [7,20,21], while the band at 1205 cm -1 is dominated by the ring vibrations of polysaccharides C-O-P, PO-P [22]. The band at 1469 cm -1 is derived from CH2 banding of the acyl chains from phospholipids [7,20,21].…”

“…For carbohydrate, the band at 1430 cm -1 is assigned to δ (CH2) of polysaccharide [7,20,21], while the band at 1205 cm -1 is dominated by the ring vibrations of polysaccharides C-O-P, PO-P [22]. The band at 1469 cm -1 is derived from CH2 banding of the acyl chains from phospholipids [7,20,21]. The band at 1620 cm -1 is assigned to stretching base carbonyl and ring breathing mode of 11 nucleic acids [19], and 1592 cm -1 is assigned to C=N and NH2 in adenine [22].…”