Characterisation of dihydroazulene and vinylheptafulvene derivatives using Raman spectroscopy: The CN-stretching region.

The effect of adding electron donating and withdrawing groups on the dihydroazulene (DHA)/vinylheptafulvene (VHF) photochromic system has been investigated using Raman spectroscopy in CS2 solutions. The photoswitching between DHA and VHF is often characterised with UV-Vis spectroscopy. However, Raman spectroscopy can also be used for this purpose and give structural insight, as the light induced ring-opening from DHA to VHF causes changes in the CN-stretching frequencies. The CN-stretching frequencies in DHA and VHF are isolated and optimal for the identification of DHA and VHF. The DHA system is also investigated in the solid state.

Stones in the lacrimal gland: a rare condition.

PURPOSE: Stones (dacryoliths) in the lacrimal drainage system are relatively common. However, stones in the lacrimal gland itself are very rare. We present three cases of lacrimal gland stones and describe the clinical and histopathological characteristics and composition of the stones. METHODS: Three patients presented with swelling in the lateral canthal region of several months' duration. Clinical examination in each case revealed a mass adjacent to the lacrimal gland. We carried out surgical excision, histological examination and Raman spectroscopy. RESULTS: Histopathological examination of the excised material showed an eosinophilic, amorphic material organized in lamellae and localized in a ductule. The findings were consistent with a stone in the lacrimal gland in all three cases. All stones were composed of proteins of similar types. After surgery, the three patients healed without complications. CONCLUSIONS: Lacrimal gland stones represent a very rare but relevant differential diagnosis when a patient presents with unilateral persistent conjunctivitis or with a tumour in the lateral canthus. Treatment is excision under local anaesthesia.

Fourier transform Raman difference spectroscopy for detection of lignin oxidation products in thermomechanical pulp.

Spruce thermomechanical pulp (TMP) was oxidized by the 2,2'azinobis-3-ethylbenzthiazoline-6-sulfonate cation radical (ABTS*+) in the presence and absence of oxygen. The pulp modification was monitored by Fourier transform (FT) Raman difference spectroscopy and other nondestructive spectroscopic methods. The ABTS*+ oxidative system resulted in modifications very similar to the laccase-ABTS-oxygen system, except for the FT-Raman results, which showed a difference in mechanisms attributed to a difference in produced Raman bands. Oxygen resulted in no oxygen-derived products, but only enhanced the production of a specific Raman band of several oxidation-produced bands. Detailed information on lignin reactions can be obtained from FT-Raman signals.

Melanoma diagnosis by Raman spectroscopy and neural networks: structure alterations in proteins and lipids in intact cancer tissue.

Melanoma is the most aggressive skin cancer. The specificity and sensitivity of clinical diagnosis varies from around 40% to 80%. Here, we investigated whether the chemical changes in the melanoma tissue detected by Raman spectroscopy and neural networks can be used for diagnostic purposes. Near-infrared Fourier transform Raman spectra were obtained from samples of melanoma (n=22) and other skin tumors that can be clinically confused with melanoma: pigmented nevi (n=41), basal cell carcinoma (n=48), seborrheic keratoses (n=23), and normal skin (n=89). A sensitivity analysis of spectral frequencies used by a neural network was performed to determine the importance of the individual components in the Raman spectra. Visual inspection of the Raman spectra suggested that melanoma could be differentiated from pigmented nevi, basal cell carcinoma, seborrheic keratoses, and normal skin due to the decrease in the intensity of the amide I protein band around 1660 cm-1. Moreover, melanoma and basal cell carcinoma showed an increase in the intensity of the lipid-specific band peaks around 1310 cm-1 and 1330 cm-1, respectively. Band alterations used in the visual inspection were also independently identified by a neural network for melanoma diagnosis. The sensitivity and specificity for diagnosis of melanoma achieved by neural network analysis of Raman spectra were 85% and 99%, respectively. We propose that neural network analysis of near-infrared Fourier transform Raman spectra could provide a novel method for rapid, automated skin cancer diagnosis on unstained skin samples.