Abstract
The surfaces of chemically synthesized spherical gold NPs (Au-NPs) have been modified using chiral L- or D-penicillamine (Pen) in order to impart enantioselective adsorption properties. These chiral Au-NPs have been used to demonstrate enantioselective adsorption of racemic propylene oxide (PO) from aqueous solution. In the past we have studied enantioselective adsorption of racemic PO on L- or D-cysteine (Cys)-coated Au-NPs. This prior work suggested that adsorption of PO on Cys-coated Au-NPs equilibrates within an hour. In this work, we have studied the effect of time on the enantioselective adsorption of racemic PO from solution onto chiral Pen/Au-NPs. Enantioselective adsorption of PO on chiral Pen/Au-NPs is time-dependent but reaches a steady state after ~18 h at room temperature. More importantly, L- or D-Pen/Au-NPs are shown to adsorb R- or S-PO enantiospecifically and to separate the two PO enantiomers from racemic mixtures of RS-PO.
Highlights
Chirality has attracted enormous interest in the field of chemistry due to the enantiospecific responses of living organisms to the two enantiomers of chiral compounds that they have ingested. These differences in response are important in pharmaceutical industries because it is often the case that only one enantiomer of a chiral drug is therapeutically active
Chiral pharmaceuticals that are produced synthetically must be prepared in enantiomerically pure form
Researchers have focused on the role of chirality in other areas such as catalysis [1], chiroptical applications [2,3], chiral magnetism [4], chiral semiconductors [5], cellular imaging [6], sensing [7], biomedical applications [8], chiral molecular assembly on surface [9], supramolecular chirality [10] and synthesis of chiral nanoparticles (NPs) [11]
Summary
Chirality has attracted enormous interest in the field of chemistry due to the enantiospecific responses of living organisms to the two enantiomers of chiral compounds that they have ingested. A number of these studies have required synthesis of nanomaterials, it is still challenging to synthesize well-defined, monodispersed and inherently chiral NPs. In previous work, we have shown that L- and D-cysteine (Cys, HO2CCH(NH2)CH2SH) modified surfaces of Au-NPs are capable of enantiospecific adsorption of racemic propylene oxide (PO) [11,12] and the chiral pharmaceutical propranolol hydrochloride [13]. We have shown that L- and D-cysteine (Cys, HO2CCH(NH2)CH2SH) modified surfaces of Au-NPs are capable of enantiospecific adsorption of racemic propylene oxide (PO) [11,12] and the chiral pharmaceutical propranolol hydrochloride [13] In these studies, Au-NPs were either spherical or tetrahexahedral (24-sided) in shape. The second direction in which this work expands on our prior accomplishments is by documenting the eTffhecet osefcaodnsdorpdtiiroenctitoimneionnwenhaicnhtiotsheilsecwtivorekadesxoprapntidosn oonf raocuermpicriRoSr-PaOccoomn pchliisrhamllyenmtsodisifiebdy Adouc-uNmPse.nItnintghethpeaset,ffeencatnotifosaedlesoctripvteioandstoirmpetioonnweansasnttuidosieedlewctiitvheinaodnsoerhpotuiornofoefxrpaocseumreicofRtSh-ePcOhiroanl NchPirsatlolythmeocdhiifriaeldpAroub-eNPPOs.[I1n1–th14e].pHasetr, ee,nwanetfiionsdeltehcattivteheadeqsourilpibtiroantiownaosfsPtuOdoiendPwenit/hAiun-oNnPerheoquurireosf ~e1x8pohsuofreexopf othsuerceh. iOraul rNwPosrtko sthhoewchsitrhalatpwrohbeenPuOsi[n1g1–P1e4n].aHs earceh, iwraelfliingdantdha, tonthlye ewqeuaiklibernaatniotinomofePrOic soenpPaerant/iAonu-oNfPPOreqisuoirbesse~rv18edhwofitehxinpoosnuereh.oOuurrowf PoOrkesxhpoowsus rteh;ahtowwheevneru,stihnegrePeisnaansaalmchoisrtalteling-afonldd, ionnclryeawseeaink eennaannttiioommeerriiccsseeppaarraattioionnaoftferPO18 ihs oofbPseOrveexdpowsuitrhei.n one hour of PO exposure; there is an almost ten-fold increase in enantiomeric separation after 18 h of PO exposure
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