With 298 heterogeneous soil samples from Yixing (Jiangsu Province), Zhongxiang and Honghu (Hubei Province), this study aimed to combine a successive projections algorithm (SPA) with a support vector machine regression (SVMR) model (SPA-SVMR model) to improve the estimation accuracy of soil organic carbon (SOC) contents using the laboratory-based visible and near-infrared (VIS/NIR, 350−2500 nm) spectroscopy of soils. The effects of eight spectra pre-processing methods, i.e., Log (1/R), Log (1/R) coupled with Savitzky-Golay (SG) smoothing (Log (1/R) + SG), first derivative with SG smoothing (FD), second derivative with SG smoothing (SD), SG, standard normal variate (SNV), mean center (MC) and multiplicative scatter correction (MSC), on SPA-based informative wavelength selection were explored. The SVMR model (i.e., SVMR without SPA) and SPA-PLSR model (i.e., SPA combined with partial least squares regression (PLSR)) were developed and compared with the SPA-SVMR model in order to evaluate the performance of SPA-SVMR. The results indicated that the variables selected by SPA and their distributions were strongly affected by different pre-processing methods, and SG was the optimal pre-processing method for SPA-SVMR model development; the SPA-SVMR model using SG pre-processing and 28 SPA-selected wavelengths obtained a better result (R 2 V = 0.73, RMSE V = 2.78 g·kg and RPD V = 1.63). Most of the spectral bands used by the SPA-SVMR model over the near-infrared region were important wavelengths for SOC content estimation. This study demonstrated that the combination of SPA and SVMR is feasible and reliable for estimating SOC content from the VIS/NIR spectra of soils in regions with multiple soil and land-use types.

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The development of novel hemostatic agents with distinct modes of action from traditional ones remains a formidable challenge. Self-assembling peptide hydrogels have emerged as a new hemostatic material, not only because of their inherent biocompatibility and biodegradability but also their designability. Especially, rational molecular design can make peptides and their hydrogelation responsive to biological cues. In this study, we demonstrated that transglutaminase-catalyzed reactions not only occurred among designed short peptide I3QGK molecules but also between the peptide and a natural polysaccharide O-carboxymethyl chitosan. Because Factor XIII in the blood can rapidly convert into activated transglutaminase (Factor XIIIa) upon bleeding, these enzymatic reactions, together with the electrostatic attraction between the two hemostatic agents, induced a strong synergetic effect in promoting hydrogelation, blood coagulation, and platelet adhesion, eventually leading to rapid hemostasis. The study presents a promising strategy for developing alternative hemostatic materials and methods.

The function and properties of peptide-based materials depend not only on the amino acid sequence but also the molecular conformations. In this paper, we chose a series of peptides G m (XXKK) n X-NH 2 (m=0, 3; n=2,3; X=I, L, and V) as the model molecules, and studied the conformation regulation through N terminus lipidation and their formulation with surfactants. The structural and morphological transition of peptide self-assemblies have also been investigated via transmission electron microscopy (TEM), atomic force microscopy (AFM), circular dichroism spectroscopy (CD), and small angle neutron scattering (SANS). With the terminal alkylation, the molecular conformation changed from random coil to β-sheet or α-helix. The antimicrobial activities of alkylated peptide were different. C 16 -G 3 (IIKK) 3 I-NH 2 showed antimicrobial activity against Streptococcus mutans while C 16 -(IIKK) 2 I-NH 2 and C 16 -G 3 (IIKK) 2 I-NH 2 didn't kill the bacteria. Surfactant sodium dodecyl sulfonate (SDS) could rapidly induce the self-assemblies of alkylated peptides (C 16 -(IIKK) 2 I-NH 2 , C 16 -G 3 (IIKK) 2 I-NH 2 , C 16 -G 3 (VVKK) 2 V-NH 2 ) from nanofibers to micelles, along with the conformation changing from β-sheet to α-helix. Cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB) made the lipopeptide nanofibers thinner, and nonionic surfactant polyoxyethylene (23) lauryl ether (C 12 EO 23 ) induced the nanofibers much more intensive. Both the activity and conformation of α helical peptide could be modulated by lipidation. Then the self-assembled morphologies of alkylated peptides could also be further regulated with surfactants through hydrophobic, electrostatic and hydrogen bonding interactions. These 3 results provided useful strategies to regulate the molecular conformations in peptide-based material functionalization.