The gas-phase structures of protonated and alkali-metal-cationized lysine (Lys) and epsilon-N-methyllysine (Lys(Me)) are investigated using infrared multiple photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser, in conjunction with ab initio calculations. IRMPD spectra of Lys.Li(+) and Lys.Na(+) are similar, but the spectrum for Lys.K(+) is different, indicating that the structure of lysine in these complexes depends on the metal ion size. The carbonyl stretch of a carboxylic acid group is clearly observed in each of these spectra, indicating that lysine is nonzwitterionic in these complexes. A detailed comparison of these spectra to those calculated for candidate low-energy structures indicates that the bonding motif for the metal ion changes from tricoordinated for Li and Na to dicoordinated for K, clearly revealing the increased importance of hydrogen-bonding relative to metal ion solvation with increasing metal ion size. Spectra for Lys(Me).M(+) show that Lys(Me), an analogue of lysine whose side chain contains a secondary amine, is nonzwitterionic with Li and zwitterionic with K and both forms are present for Na. The proton affinity of Lys(Me) is 16 kJ/mol higher than that of Lys; the higher proton affinity of a secondary amine can result in its preferential protonation and stabilization of the zwitterionic form. 相似文献
The efficiency of formation of protonated heterotrimers of lysine with underivatised sugars (mono-, di-, and trisaccharides) and N-acetylglucosamine (N-AcGlc) was studied under electrospray ionisation conditions. The collision induced dissociation spectra of [Lys + sugar + NAcGlc + H](+) resulted in [Lys + NAcGlc + H](+) and [Lys + sugar + H](+) as the major product ions. Relative abundances of these two fragments reflect the extent of adduct formation of protonated lysine plus sugar, with reference to the reference compound NAcGlc. This relative abundance ratio was found to be characteristic of the sugar structure. In this way it was observed that the ability of lysine to form a protonated heterodimer with neutral sugars increases with an increase in the number of acetal oxygens. Lactose showed an anomalously high affinity for protonated Lys, possibly reflecting the axial hydroxyl at C4. The postulated involvement of the epsilon-NH(2) group of lysine in the formation of protonated heterodimers with sugars was supported by similar results of similar experiments with NH(3) in place of lysine. 相似文献
Gold nanoparticles are potentially very attractive components for therapeutic delivery since they can be synthesized with any diameter from 1 to 200 nm to carry a payload of therapeutic molecules into a cell without triggering an immune response. Gold nanoparticles must undergo surface transformations before coupling to therapeutic molecules to become eligible for this purpose. It is now more understood that amine groups can bind to gold nanoparticles strongly, which has enabled surface modification of gold nanoparticles with amino acid lysine through its amine group. These lysine capped gold nanoparticles can further be coupled to therapeutic molecules for delivery purposes. In this study gold nanoparticles were first synthesized and capped with lysine molecules. TEM and FTIR measurements demonstrated the synthesis of lysine-capped gold nanoparticles with an average diameter of 10 nanometers. Interferon alpha molecules-one of the most important therapeutic protein were then chemically bound to lysine-capped gold nanoparticles through a two-step process of diimide-activated amidation. The conjugation of interferon molecules to lysine capped gold nanoparticles was carried out via the reaction between the free amine group of lysine and carboxyl groups of interferon using N-ethyl-N′-13-dimethyl-aminopropyl (EDAC) as a coupling agent. The process of conjugation has also been studied by transmission electron microscopy. 相似文献
Upon hexanal-modification in the presence of NaCNBH(3), the oxidized B chain of insulin becomes mono- and further dialkylated on both the N-terminal and Lys(29) residues. A pseudo-MS(3) study was performed with a triple-quadrupole mass spectrometer on the different modified lysine-containing species to gain further insights into the characteristic fragmentation pattern. These fragmentations, in good agreement with true MS(3) measurements obtained using an ion trap mass spectrometer, highlighted characteristic monoalkylated lysine (immonium-NH(3)) and protonated modified caprolactam ions at m/z 168 and 213, respectively. In contrast, no fragment ion derived from a modified lysine residue (immonium or caprolactam) was observed when dialkylation occurs on Lys(29). However, a fragment ion corresponding to a protonated dihexylamine was observed at m/z 186. This loss, characteristic of dialkylated lysine fragmentation, was also observed upon dialkylation of N(alpha)-acetyllysine with either hexanal or pentanal. On the other hand, acetylation and malondialdehyde-modification of the N(alpha)-acetyllysine side chain led mainly to the corresponding modified (immonium-NH(3)) fragment ions at m/z 126 and 138, respectively. Finally, it was demonstrated that precursor ion scanning for both m/z 168 and 213 ions led to specific and sensitive identification of peptides containing hexanal-modified lysine residues within an unfractionated tryptic digest of hexanal-modified apomyoglobin. Thus, Lys(42), Lys(45), Lys(62), Lys(63), Lys(77), Lys(87), Lys(96), Lys(98), Lys(145) and Lys(147) were found to be modified upon reaction with hexanal. 相似文献
Five 42-residue polypeptides have been designed to fold into hairpin helix-loop-helix motifs that dimerize to form four-helix bundles, and to serve as protein scaffolds for the elucidation at the molecular level of the principles that control and fine-tune lysine and ornithine reactivities in a protein context. Site-selective control of Lys and Orn reactivity provides a mechanism for addressing directly individual residues and is a prerequisite for the site-selective functionalization of folded proteins. Several lysine and one ornithine residues were introduced on the surface and in the hydrophobic core of the folded motif. The reactivity of each residue was determined by measuring the degree of acylation of the trypsin cleaved fragments by HPLC and mass spectrometry. The most reactive residues were Orn34 and Lys19, both of which were located in d positions in the heptad repeat, and therefore in hydrophobic environments. Upon reaction of the helix-loop-helix dimer KA-I with one equivalent of mono-p-nitrophenyl fumarate, Orn34 was acylated approximately three times more efficiently than Lys19, whereas Lys10 (b position), Lys15 (g position), and Lys33 (c position) remained unmodified. In the sequence KA-I-A(15) Lys15 was replaced by an alanine residue and the selectivity of Orn34 over Lys19 increased to approximately a factor of six, probably because Lys15 had the capacity to reduce the pK(a) value of Lys19 and 85 % of site-selectively monoacylated product was obtained. The pH dependence of the acylation reaction was determined and showed that the pK(a) of the reactive residues were 9.3, more than a pK(a) unit below the magnitude of the corresponding residue in a solvent exposed position. Introducing Lys and Orn residues into a or d positions of the heptad repeat therefore serves as a mechanism of depressing their pK(a) to increase their reactivity site selectively. Extensive NMR and CD spectroscopic analyses showed that the sequences fold according to prediction. 相似文献
In this communication, solid-phase reactions for the synthesis of Lys-monofunctionalized gold nanoparticles are described. A controlled and selective fabrication of linear nanoparticle arrays can be achieved through peptide linkage systems, and therefore it is essential to prepare Fmoc amino acid nanoparticle building blocks susceptible to Fmoc solid-phase peptide synthesis. Gold nanoparticles containing carboxylic acids (2) in the organic shell were covalently ligated to Lys on solid supports through amide bond coupling reactions. We employed Fmoc-Lys-substituted polymer resins such as Fmoc-Lys-Wang or Fmoc-Lys-HMPA-PEGA. The low density of Lys on the matrix enabled 2 nm-sized gold nanoparticles to react with Lys in a 1:1 ratio. Subsequent cleavage reactions using 60% TFA reagent resulted in Lys transfer from the solid matrix to gold nanoparticles, and the Fmoc-Lys-monofunctionalized gold nanoparticles (5) were obtained with 3-15% yield. Synthesis using HMPA-PEGA resin increased productivity due to the superior swelling properties of PEGA resin in DMF. Monofunctionalization of nanoparticles was microscopically characterized using TEM for the ethylenediamine-bridged nanoparticle dimers (6). By counting the number of 6, we found that at least 60% of cleaved nanoparticles were monofunctionalized by Lys. This method is highly selective and efficient for the preparation of monofunctionalized nanoparticles. 相似文献
Catalyzing the covalent modification of aliphatic amino groups, such as the lysine (Lys) side chain, by nucleic acids has been challenging to achieve. Such catalysis will be valuable, for example, for the practical preparation of Lys‐modified proteins. We previously reported the DNA‐catalyzed modification of the tyrosine and serine hydroxy side chains, but Lys modification has been elusive. Herein, we show that increasing the reactivity of the electrophilic reaction partner by using 5′‐phosphorimidazolide (5′‐Imp) rather than 5′‐triphosphate (5′‐ppp) enables the DNA‐catalyzed modification of Lys in a DNA‐anchored peptide substrate. The DNA‐catalyzed reaction of Lys with 5′‐Imp is observed in an architecture in which the nucleophile and electrophile are not preorganized. In contrast, previous efforts showed that catalysis was not observed when Lys and 5′‐ppp were used in a preorganized arrangement. Therefore, substrate reactivity is more important than preorganization in this context. These findings will assist ongoing efforts to identify DNA catalysts for reactions of protein substrates at lysine side chains. 相似文献
There is growing demand for novel methods that could render the controlled disassembly of higher-order structures formed, for example, by peptides. Herein, we demonstrate such a method based on the application of a photocaged variant of the amino acid lysine, namely, lys(Nvoc). Specifically, we introduce lys(Nvoc) into the primary sequence of the amyloidogenic peptide, Aβ(16-22), at a position where the native side chain is known to play a key role in fibril formation via hydrophobic interactions. Both AFM and infrared spectroscopic measurements indicate that the resultant Aβ(16-22) mutant is able to form fibrils whereas, more importantly, the fibrils thus formed can be completely disassembled upon irradiation with near-UV light, which cleaves the photolabile Nvoc moiety and triggers the restoration of the lysine side chain. These results suggest that the generation of a single charge in a highly hydrophobic region of the fibrils is sufficient to promote their dissociation. Thus, we envisage that the current approach will find useful applications wherein controlled structural disassembly or content release is required. 相似文献
We report on the use of quercetin-functionalized gold nanoparticles (QC-AuNPs) as a colorimetric probe for the amino acids arginine (Arg), histidine (His) and lysine (Lys). The method is based on the aggregation of the QC-AuNPs that is caused by these amino acids and leads to a visually detectable color change from red to blue. The absorption maxima shift from 525 nm to 702, 693, and 745 nm, respectively. Aggregations are confirmed by dynamic light scattering (DLS) and transmission electron microscopic techniques (TEM). The effects of the QC concentration, temperature and reaction time for the preparation of QC-Au NPs were tested. Other amino acids do not interfere. Under the optimal conditions, linear relationships exist between the absorption ratios at 702/525 nm (for Arg), 693/525 nm (for His), and 745/525 nm (for Lys) over the concentrations ranges from 2.5–1,250 μM (Arg) and 1–1,000 μM (His and Lys), respectively. The respective limits of detection are 0.04, 0.03, and 0.02 μM. The method provides a useful tool for the rapid visual and instrumental determination of the three amino acids.
The interaction of lysozyme(Lys) and gold nanoparticles was investigated via UV-vis absorption and resonance light-scattering method.There are some changes of the plasmon absorption and resonance light-scattering of gold nanoparticles that were observed via the addition of Lys.The normalized plasmon absorption and resonance light-scattering intensity with gold nanoparticles were both linear wilh 1-20 nmol/L Lys.A simple model about the component of the gold nanoparticles and Lys complex was established and the calculated result was fitted well in their concentration ratio.Furthermore,the activity analysis of Lys showed that the interaction was weak and nondestructive. 相似文献