Lime is widely used to modify clayey soils to enhance their physical and chemical properties,and lime-treated soil has become a key material in transportation infrastructure.Chemical reactions were identified through ...Lime is widely used to modify clayey soils to enhance their physical and chemical properties,and lime-treated soil has become a key material in transportation infrastructure.Chemical reactions were identified through laboratory tests from field samples collected from the subgrade after 30 years of operation to understand its long-term performance evolution.Exchangeable calcium,carbonated calcium,and total calcium were quantified using ethylenediaminetetraacetic acid(EDTA)titration,gasometric analysis,and the strong acid extraction method,respectively.These measurements enabled the evaluation of calcium transformation during the pozzolanic reaction,providing a quantitative characterization of pozzolanic progression in the lime-treated clay matrix.Evolutions in pH,electrical conductivity,and salinity were also tracked.Mechanical performance was assessed through maximal shear modulus(Gmax)and unconfined compressive strength(UCS)tests.Then,the microstructure and mineral composition were analyzed via scanning electron microscopy(SEM)and X-ray diffraction(XRD).Furthermore,with an extended curing period,the pH,electrical conductivity,salinity,and exchangeable calcium content were found to decrease gradually.In contrast,the carbonation-related calcium content increased,and the clay mineral structures were significantly altered.The significant increase in Gmax and UCS is attributed to the formation of calcium-aluminate-silicate-hydrate(C-(A)-S-H)for pozzolanic and carbonation reactions where the clay mineral is involved.SEM reveals the curled edges of clay minerals and the formation of a 3D network.Additionally,XRD patterns further confirm the presence of increasing amounts of amorphous phases within the 2θrange of 15°–32°,indicating the progression of the pozzolanic reaction.展开更多
Cyclodepsipeptides represent a distinctive family of natural cyclic peptides endowed with diverse and potent biological activities,making them promising scaffolds for drug development and agrochemical applications.Inc...Cyclodepsipeptides represent a distinctive family of natural cyclic peptides endowed with diverse and potent biological activities,making them promising scaffolds for drug development and agrochemical applications.Incorporation of N-methylated amino acids further enhances their metabolic stability and oral bioavailability by resisting proteolytic degradation.However,the synthesis of such cyclodepsipeptides,especially those containing multiple sterically hindered N-methylated residues,remains a significant challenge for conventional solid-phase peptide synthesis(SPPS)due to inefficient on-resin acylation,sluggish coupling kinetics,and conformational constraints.Herein,we report the first successful application of a novel solid-phase peptide synthesis(SPPS)strategy based on immobilized ribosome-mimicking molecular reactors(RMMRs)for the efficient synthesis of two representative bioactive cyclodepsipeptides:destruxin B(a hexadepsipeptide with two consecutive N-methylated amino acids)and[2S,3S-Hmp]-aureobasidin L(a nonapeptide featuring four N-methylated amino acids).A crucial approach is the use of pre-assembled depsidipeptide building blocks,which mitigate side reactions associated with on-resin esterification,combined with the RMMR platform that accelerates the coupling of sterically hindered residues via an artificial pseudo-intramolecular acyl-transfer mechanism.The linear precursors were efficiently assembled on Oxyma-C RMMR-HMPA resin with high/moderate crude purities(90%for destruxin B,45% for[2S,3S-Hmp]-aureobasidin L)and much reduced synthesis times(≈15 h and≈60 h,respectively).Subsequent solution-phase macrocyclization using HATU/DIPEA yielded the target compounds in satisfactory yields(75% for destruxin B,50% for[2S,3S-Hmp]-aureobasidin L).This robust and time-economic methodology overcomes key limitations of conventional methods,providing a broadly applicable platform for the synthesis of complex cyclodepsipeptides and facilitating future medicinal chemistry exploration of this valuable class of bioactive molecules.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42302311)the ARC Discovery Project Program(Grant Nos.DP210100437 and DP230100126).
文摘Lime is widely used to modify clayey soils to enhance their physical and chemical properties,and lime-treated soil has become a key material in transportation infrastructure.Chemical reactions were identified through laboratory tests from field samples collected from the subgrade after 30 years of operation to understand its long-term performance evolution.Exchangeable calcium,carbonated calcium,and total calcium were quantified using ethylenediaminetetraacetic acid(EDTA)titration,gasometric analysis,and the strong acid extraction method,respectively.These measurements enabled the evaluation of calcium transformation during the pozzolanic reaction,providing a quantitative characterization of pozzolanic progression in the lime-treated clay matrix.Evolutions in pH,electrical conductivity,and salinity were also tracked.Mechanical performance was assessed through maximal shear modulus(Gmax)and unconfined compressive strength(UCS)tests.Then,the microstructure and mineral composition were analyzed via scanning electron microscopy(SEM)and X-ray diffraction(XRD).Furthermore,with an extended curing period,the pH,electrical conductivity,salinity,and exchangeable calcium content were found to decrease gradually.In contrast,the carbonation-related calcium content increased,and the clay mineral structures were significantly altered.The significant increase in Gmax and UCS is attributed to the formation of calcium-aluminate-silicate-hydrate(C-(A)-S-H)for pozzolanic and carbonation reactions where the clay mineral is involved.SEM reveals the curled edges of clay minerals and the formation of a 3D network.Additionally,XRD patterns further confirm the presence of increasing amounts of amorphous phases within the 2θrange of 15°–32°,indicating the progression of the pozzolanic reaction.
基金National Natural Science Foundation(No.22450003)Jiangsu Province Natural Science Foundation Basic Research Program(No.BK20253010).
文摘Cyclodepsipeptides represent a distinctive family of natural cyclic peptides endowed with diverse and potent biological activities,making them promising scaffolds for drug development and agrochemical applications.Incorporation of N-methylated amino acids further enhances their metabolic stability and oral bioavailability by resisting proteolytic degradation.However,the synthesis of such cyclodepsipeptides,especially those containing multiple sterically hindered N-methylated residues,remains a significant challenge for conventional solid-phase peptide synthesis(SPPS)due to inefficient on-resin acylation,sluggish coupling kinetics,and conformational constraints.Herein,we report the first successful application of a novel solid-phase peptide synthesis(SPPS)strategy based on immobilized ribosome-mimicking molecular reactors(RMMRs)for the efficient synthesis of two representative bioactive cyclodepsipeptides:destruxin B(a hexadepsipeptide with two consecutive N-methylated amino acids)and[2S,3S-Hmp]-aureobasidin L(a nonapeptide featuring four N-methylated amino acids).A crucial approach is the use of pre-assembled depsidipeptide building blocks,which mitigate side reactions associated with on-resin esterification,combined with the RMMR platform that accelerates the coupling of sterically hindered residues via an artificial pseudo-intramolecular acyl-transfer mechanism.The linear precursors were efficiently assembled on Oxyma-C RMMR-HMPA resin with high/moderate crude purities(90%for destruxin B,45% for[2S,3S-Hmp]-aureobasidin L)and much reduced synthesis times(≈15 h and≈60 h,respectively).Subsequent solution-phase macrocyclization using HATU/DIPEA yielded the target compounds in satisfactory yields(75% for destruxin B,50% for[2S,3S-Hmp]-aureobasidin L).This robust and time-economic methodology overcomes key limitations of conventional methods,providing a broadly applicable platform for the synthesis of complex cyclodepsipeptides and facilitating future medicinal chemistry exploration of this valuable class of bioactive molecules.
