Study on Raman spectra of two expansins in pure solid-phase and in water solutions

The Raman spectra of two kinds of expansins KT-30 and DA-6 are measured and analyzed in the cases of pure solid-phase and in water solutions. The results show that, KT-30 has much richer and narrower Raman spectral peaks. The first, second, and third strong Raman peaks are respectively located 990.68738 cm−1, 1606.0975 cm−1, and 1327.9379 cm−1. Besides the dense and narrow Raman peaks below 1800 cm−1, there exist three weak peaks within 3050–3410 cm−1. In comparison, fewer spectral peaks can be observed for DA-6. The first and second strong peaks respectively appear at 2883.03760 cm−1 and 2848.4480 cm−1. There exist about 8 peaks below 1500 cm−1. In water solutions, bell-shaped and homogeneous fluorescence background will respectively superpose on the Raman spectra of KT-30 and DA-6 within 100–2500 cm−1 and 400–4000 cm−1. Parts of spectral peaks will be covered accordingly. Moreover, the peak position shifts of KT-30 are very slight. While DA-6 takes the opposite. Its largest shift can even be up to 63.4148 cm−1. The results can supply important fingerprint data for Raman detection of expansins in fruits and vegetables.