The　27　mer　DNA　aptamer　for　adenosine　and　adenosine　5＇-triphosphate　(ATP)　is　a　popular　model　system　for　designing　biosensors.　Various　strategies　have　been　reported　for　1　bel-free　colorimetric　detection　using　gold　nanoparticles　(AuNPs).　It　is　generally　accepted　that　free　aptamers　can　protect　AuNPs　against　salt-induced　aggregation,　whereas　target-bound　aptamers　cannot.　However,　these　studies　only　considered　the　aptamer　binding　to　its　target,　and　the　adsorption　of　the　aptamer　on　AuNPs,　but　none　considered　the　adsorption　of　target　molecules　by　AuNPs.　We　herein　report　that　the　adsorption　of　adenosine　destabilized　citrate-capped　AuNPs　with　an　apparent　K-d　Of　just　7.7　mu　M　adenosine,　whereas　that　of　ATP　stabilized　the　AuNPs　because　of　the　negative　charges　from　the　triphosphate　group.　The　adsorbed　ATP　inhibited　the　adsorption　of　DNA.　Using　the　aptamer　and　a　nonbinding　mutant,　ATP　and　guanosine　5＇-triphosphate　(GTP)　had　the　same　colorimetric　response,　and　so　did　adenosine　and　guanosine,　regardless　of　the　DNA　sequence,　indicating　that　the　color　change　mainly　reflected　the　adsorption　of　the　nucleosides　and　nucleotides　instead　of　aptamer　binding.　The　related　literature　examples　using　this　aptamer　were　classified　into　three　types　and　individually　analyzed,　where　the　reported　color　changes　can　all　be　explained　by　the　adsorption　of　target　analytes.