Conformational study and reassessment of the vibrational assignments for Norspermidine

The present study presents and discusses the conformational preferences of Norspermidine (NSpd). The effects of varying the dielectric constant on the conformational preferences are discussed, with a view to infer which conformation will correspond to the most stable in the pure condensed liquid phase. Within the same context, a set of NSpd-NH3 molecular adducts were simulated in order to determine the relevance of intermolecular hydrogen bonding on the overall stability and relative positioning of the respective vibrational frequencies. The calculations presently performed allowed a reassessment of the vibrational assignments for NSpd. A full assignment of the NSpd vibrational spectra is presented, with special emphasis being given to the vibrational modes that proved to be most affected by hydrogen bonding. The various inconsistencies of a prior study found in the literature were identified and rectified

Helianthus tuberosus and polyamine research: past and recent applications of a classical growth model

The earlieststudiesconcerningpolyamines(PAs)inplantswereperformedbyusing in vitro cultured explantsof Helianthustuberosus dormanttuber.Thisparenchymatissuewasparticularlyusefulduetoits susceptibility toseveralgrowthsubstances,includingPAs.Duringtuberdormancy,PAlevelsaretoolowto sustaincelldivision;thus Helianthus representsanaturalPA-deficient model.Whencultivated in vitro in the presenceofauxins, Helianthus tuber dormantparenchymacellsattheG0 stage starttodivide synchronously acquiringmeristematiccharacteristics.Therequirementforauxinstoinducecelldivision can besubstitutedbyaliphaticPAssuchasputrescine,spermidineorspermine.Cylindersorslicesof explantedhomogeneoustuberparenchymawereculturedinliquidmediumforshort-termstudiesonthe cell cycle,oronsolidagarmediumforlong-termexperiments.Morphologicalandphysiologicalmodificationsofsynchronouslydividingcellswerestudiedduringthedifferentphasesofthecellcycleinrelat on to PAsbiosynthesisandoxidation.Long-termexperimentsledtotheidentification ofthePAsasplant growthregulators,asthesolenitrogensource,astuberstoragesubstancesandasessentialfactorsfor morphogeneticprocessesandcellhomeostasis.Morerecentlythissystemwasusedtostudytheeffectson plant cellproliferationofplatinum-orpalladium-deriveddrugs(cisplatinandplatinumorpalladiumbi- substitutedspermine)thatareusedinhumancancercelllinesasantiproliferativeandcytotoxicagents. CisplatinwasthemostactivebothincellproliferationinhibitionandonPAmetabolism.Similarexperi- ments wereperformedusingthreeagmatineanalogous.Differenteffectsofthesecompoundswere observedoncellproliferation,freePAlevelsandenzymeactivities,leadingtoahypothesisofacorrelation between theirchemicalstructureandtheagmatinemetabolisminplant