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In this paper, the performance of a smooth nonlinear energy sink (NES) to mitigate vibration of a rotating beam under an external force is investigated. The rotating beam is modeled using the Euler-Bernoulli beam theory, and the centrifugal stiffening effect is considered. It is assumed that the nonlinear energy sink has a linear damping and an essentially nonlinear (nonlinearizable or cubic) stiffness. Required conditions for occurring Hopf bifurcation, saddle-node bifurcation and strongly modulated responses (SMR) in the system are investigated. The most important parameter to study NES performance is SMR occurrence range in the detuning parameter span. Effects of position and damping of the NES and magnitude of the external force on the vibration mitigation of the rotating beam are studied. The Complexification-Averaging and the Runge Kutta methods are employed for analytical and numerical investigations, respectively. Finally, the efficiency of an optimal linear absorber and an optimal NES in the vibration mitigation of the rotating beam are compared. It is shown that the best range for the parameters of the NES is the one in which SMR and weak modulated response occur simultaneously. Furthermore, the best position for connecting the NES to a rotating beam is at the beam tip. [ABSTRACT FROM AUTHOR]

YcjN is a putative substrate binding protein expressed from a cluster of genes involved in carbohydrate import and metabolism in Escherichia coli. Here, we determine the crystal structure of YcjN to a resolution of 1.95 Å, revealing that its three-dimensional structure is similar to substrate binding proteins in subcluster D-I, which includes the well-characterized maltose binding protein. Furthermore, we found that recombinant overexpression of YcjN results in the formation of a lipidated form of YcjN that is posttranslationally diacylated at cysteine 21. Comparisons of size-exclusion chromatography profiles and dynamic light scattering measurements of lipidated and nonlipidated YcjN proteins suggest that lipidated YcjN aggregates in solution via its lipid moiety. Additionally, bioinformatic analysis indicates that YcjN-like proteins may exist in both Bacteria and Archaea, potentially in both lipidated and nonlipidated forms. Together, our results provide a better understanding of the aggregation properties of recombinantly expressed bacterial lipoproteins in solution and establish a foundation for future studies that aim to elucidate the role of these proteins in bacterial physiology., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

This study shows the enhancement of glass ionomer cement (GIC) by incorporating hydroxyapatite (HA) and zinc oxide (ZnO) nanoparticles to improve its mechanical strength, biological activity, and antibacterial properties. GC is widely used in dental and orthopedic applications due to its bioactivity and biocompatibility, but it suffers from weak antibacterial properties and limited load-bearing capacity. HA, a calcium phosphate compound similar to natural bone, and ZnO, known for its antibacterial and bone-regenerative properties, were integrated into GIC to address these limitations. The modified GC exhibited improved compressive strength and bioactivity, particularly with the addition of 4 wt% ZnO nanoparticles, which showed the highest increase in mechanical performance while maintaining cytocompatibility. However, the fluoride release was reduced, indicating an exchange between enhanced mechanical properties and fluoride ion release. Antibacterial efficacy was assessed using well diffusion, MIC, and MBC tests, confirming that the modified GC has significant potential in dental and orthopedic applications. Future research should focus on the long-term effects of Zn 2 ⁺ ion release to fully understand its impact on the antibacterial performance of the cement., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier Ltd.)

Medium-sized rings (8-11-membered cycles) are often more challenging to synthesize than smaller rings (5-7-membered cycles) due to ring strain. Herein, we report a catalytic method for forming 8- and 9-membered rings that proceeds via the intramolecular Friedel-Crafts reactions of vinyl carbocation intermediates. These reactive species are generated catalytically through the ionization of vinyl toluenesulfonates by a Lewis acidic lithium cation-weakly coordinating anion salt.

In recent years, bone materials and cement innovation have made extraordinary strides. Calcium phosphate cement (CPC) regenerates body tissues and repairs bone and dental defects. Since the presence of nanoparticles (NPs) increased the initial cement strength in terms of the reduction of porosity, magnesium (Mg) NPs were used because of their unique properties. In this study, the effects of various Mg NP percentages and sizes on reinforced cement thermal behavior and mechanical behavior are investigated using the molecular dynamics (MD) simulation method. The changes of Young's modulus (YM), maximum temperature (MT), and ultimate strength (US) were investigated for this reason. The US, YM, and MT of the reinforced cement sample improved from 0.879 to 0.171 MPa to 1.326 and 0.255 MPa, respectively, and from 1321 to 1403 K by raising the NPs percentage to 4%. The radius increase of NPs to 16 Å enhanced the US, YM, and MT to 0.899 MPa, 0.179 MPa, and 1349 K. The MT decreased to 1275 K. The quantity and size of the Mg NPs significantly enhanced the mechanical behavior of the finished cement, according to the findings., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors. Published by Elsevier Ltd.)

This study used the molecular dynamics (MD) simulation method to assess the effects of different percentages of NPs, sizes, and percentages of porosity on reinforced cement thermal behavior (TB) and mechanical behavior (MB) of samples. The temperature and kinetic energy (KE) converged to 300 K and 35.42 eV after 10 ns, which indicated the thermodynamic equilibrium and the atomic stability in the structures. Increasing the NPs percentage from 1% to 3% increased the maximum temperature from 1364 to 1405 K. By further increasing it to 5%, it was reduced to 1361 K. As the radius of Zn NPs increased to 16 Å, the ultimate strength (US) and Young's Modulus (YM) increased from 1.07 to 0.19 MPa to 1.2 and 0.22 MPa. The increase in the NPs' radius to 16 Å caused an increase in the maximum temperature from 1405 to 1455 K, maintaining atomic stability. As the porosity increased from 1% to 5%, the US and YM reduced from 0.91 to 0.17 MPa to 0.81 and 0.15 MPa. As the porosity increased from 1% to 5%, the maximum temperature was reduced from 1400 K to 1384 K. According to the results, Zn NPs' percentage and size effectively improved the MB of the final cement., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The SARS-CoV-2 main protease (M pro ) is responsible for cleaving twelve nonstructural proteins from the viral polyprotein. M pro , a cysteine protease, is characterized by a large number of noncatalytic cysteine (Cys) residues, none involved in disulfide bonds. In the absence of a tertiary-structure stabilizing role for these residues, a possible alternative is that they are involved in redox processes. We report experimental work in support of a proposal that surface cysteines on M pro can protect the active-site Cys145 from oxidation by reactive oxygen species (ROS). In investigations of enzyme kinetics, we found that mutating three surface cysteines to serines did not greatly affect activity, which in turn indicates that these cysteines could protect Cys145 from oxidative damage., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Investigation of cortical bone using magnetic resonance imaging is a developing field, which uses short/ultrashort echo time (TE) pulse sequences to quantify bone water content and to obtain indirect information about bone microstructure., Purpose: To improve the accuracy of the previously proposed technique of free water T 1 quantification and to seek the relationship between cortical bone free water T 1 and its mechanical competence., Study Type: Prospective., Subjects: Twenty samples of bovine tibia bone., Field Strength/sequences: 3.0 T; ultra-fast two-dimensional gradient echo, Radio frequency-spoiled three-dimensional gradient echo., Assessment: Cortical bone free water T 1 was quantified via three different methods: inversion recovery (IR), variable flip angle (VFA), and variable repetition time (VTR). Signal-to-noise ratio was measured by dividing the signal of each segmented sample to background noise. Segmentation was done manually. The effect of noise on T 1 quantification was evaluated. Then, the samples were subjected to mechanical compression test to measure the toughness, yield stress, ultimate stress, and Young modulus., Statistical Tests: All the statistical analysis (Shapiro-Wilk, way analysis of variance, paired t test, Pearson correlation, and Bland-Altman plot) were done using SPSS., Results: Significant difference was found between T 1 quantification groups (P < 0.05). Average T 1 of each quantification method differed significantly after adding noise (P < 0.05). VFA-T 1 values significantly correlated with toughness (r = -0.68, P < 0.05), ultimate stress (r = -0.71, P < 0.05), and yield stress (r = -0.62, P < 0.05). No significant correlation was found between VTR-T 1 values and toughness (P = 0.07), ultimate stress (P = 0.47), yield stress (P = 0.30), and Young modulus (P = 0.39)., Data Conclusion: Pore water T 1 value is associated with bone mechanical competence, and VFA method employing short-TE pulse sequence seems a superior technique to VTR method for this quantification., Level of Evidence: 2 TECHNICAL EFFICACY: 1., (© 2021 International Society for Magnetic Resonance in Medicine.)

NmMetQ is a substrate-binding protein (SBP) from Neisseria meningitidis that has been identified as a surface-exposed candidate antigen for meningococcal vaccines. However, this location for NmMetQ challenges the prevailing view that SBPs in Gram-negative bacteria are localized to the periplasmic space to promote interaction with their cognate ABC transporter embedded in the bacterial inner membrane. To elucidate the roles of NmMetQ, we characterized NmMetQ with and without its cognate ABC transporter (NmMetNI). Here, we show that NmMetQ is a lipoprotein (lipo-NmMetQ) that binds multiple methionine analogs and stimulates the ATPase activity of NmMetNI. Using single-particle electron cryo-microscopy, we determined the structures of NmMetNI in the presence and absence of lipo-NmMetQ. Based on our data, we propose that NmMetQ tethers to membranes via a lipid anchor and has dual function and localization, playing a role in NmMetNI-mediated transport at the inner membrane and moonlighting on the bacterial surface., Competing Interests: NS, MS, EK, JL, DV, AL, DR No competing interests declared, (© 2021, Sharaf et al.)

Purpose: The purpose of our study was to use Dual-TR STE-MR protocol as a clinical tool for cortical bone free water quantification at 1.5 T and validate it by comparing the obtained results (MR-derived results) with dehydration results., Methods: Human studies were compliant with HIPPA and were approved by the institutional review board. Short Echo Time (STE) MR imaging with different Repetition Times (TRs) was used for quantification of cortical bone free water T 1 (T 1 free) and concentration (ρ free ). The proposed strategy was compared with the dehydration technique in seven bovine cortical bone samples. The agreement between the two methods was quantified by using Bland and Altman analysis. Then we applied the technique on a cross-sectional population of thirty healthy volunteers (18F/12M) and examined the association of the biomarkers with age., Results: The mean values of ρ free for bovine cortical bone specimens were quantified as 4.37% and 5.34% by using STE-MR and dehydration techniques, respectively. The Bland and Altman analysis showed good agreement between the two methods along with the suggestion of 0.99% bias between them. Strong correlations were also reported between ρ free (r 2  = 0.62) and T 1free and age (r 2  = 0.8). The reproducibility of the method, evaluated in eight subjects, yielded an intra-class correlation of 0.95., Conclusion: STE-MR imaging with dual-TR strategy is a clinical solution for quantifying cortical bone ρ free and T 1free ., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Introduction: Quantitative computed tomography (QCT) can supplement dual x-ray absorptiometry by enabling geometric and compartmental bone assessments. Whole-body spiral CT scanners are widely available and require a short scanning time of seconds, in contrast to peripheral QCT scanners, which require several minutes of scanning time. This study designed and evaluated the accuracy and precision of a homemade QCT calibration phantom using a whole-body spiral CT scanner., Materials and Methods: The QCT calibration phantom consisted of K 2 HPO 4 solutions as reference. The reference material with various concentrations of 0, 50, 100, 200, 400, 1000, and 1200 mg/cc of K 2 HPO 4 in water were used. For designing the phantom, we used the ABAQUS software., Results: The phantoms were used for performance assessment of QCT method through measurement of accuracy and precision errors, which were generally less than 5.1% for different concentrations. The correlation between CT numbers and concentration were close to one (R 2 = 0.99)., Discussion: Because whole-body spiral CT scanners allow central bone densitometry, evaluating the accuracy and precision for the easy to use calibration phantom may improve the QCT bone densitometry test., Conclusion: This study provides practical directions for applying a homemade calibration phantom for bone mineral density quantification in QCT technique., (Copyright © 2018. Published by Elsevier Inc.)

Recent work has highlighted the potential of metallocorroles as versatile platforms for the development of drugs and imaging agents, since the bioavailability, physicochemical properties and therapeutic activity can be dramatically altered by metal ion substitution and/or functional group replacement. Significant advances in cancer treatment and imaging have been reported based on work with a water-soluble bis-sulfonated gallium corrole in both cellular and rodent-based models. We now show that cytotoxicities increase in the order Ga < Fe < Al < Mn < Sb < Au for bis-sulfonated corroles; and, importantly, that they correlate with metallocorrole affinities for very low density lipoprotein (VLDL), the main carrier of lipophilic drugs. As chemotherapeutic potential is predicted to be enhanced by increased lipophilicity, we have developed a novel method for the preparation of cell-penetrating lipophilic metallocorrole/serum-protein nanoparticles (NPs). Cryo-TEM revealed an average core metallocorrole particle size of 32 nm, with protein tendrils extending from the core (conjugate size is ~100 nm). Optical imaging of DU-145 prostate cancer cells treated with corrole NPs (≤100 nM) revealed fast cellular uptake, very slow release, and distribution into the endoplasmic reticulum (ER) and lysosomes. The physical properties of corrole NPs prepared in combination with transferrin and albumin were alike, but the former were internalized to a greater extent by the transferrin-receptor-rich DU-145 cells. Our method of preparation of corrole/protein NPs may be generalizable to many bioactive hydrophobic molecules to enhance their bioavailability and target affinity.

Derivatives of the fully twisted bicyclic amide 7-hypoquinuclidone are synthesized using a Schmidt-Aubé reaction. Their structures were unambiguously confirmed by X-ray diffraction analysis and extensive spectroscopic characterization. Furthermore, the stability and chemical reactivity of these anti-Bredt amides are investigated. 7-Hypoquinuclidonium tetrafluoroborate is shown to decompose to a unique nitrogen bound amide-BF3 complex of 7-hypoquinuclidone under anhydrous conditions and to react instantaneously with water making it one of the most reactive amides known to date.

RNA interference (RNAi) mediated by small interfering RNAs (siRNAs) enables knockdown of a gene of choice, executing the logical operation: silence gene Y. The fact that the siRNA is constitutively active is a significant limitation, making it difficult to confine knockdown to a specific locus and time. To achieve spatiotemporal control over silencing, we seek to engineer small conditional RNAs (scRNAs) that mediate 'conditional RNAi' corresponding to the logical operation: if gene X is transcribed, silence independent gene Y. By appropriately selecting gene X, knockdown of gene Y could then be restricted in a tissue- and time-specific manner. To implement the logic of conditional RNAi, our approach is to engineer scRNAs that, upon binding to mRNA 'detection target' X, perform shape and sequence transduction to form a Dicer substrate targeting independent mRNA 'silencing target' Y, with subsequent Dicer processing yielding an siRNA targeting mRNA Y for destruction. Toward this end, here we design and experimentally validate diverse scRNA mechanisms for conditional Dicer substrate formation. Test tube studies demonstrate strong OFF/ON conditional response, with at least an order of magnitude increase in Dicer substrate production in the presence of the cognate mRNA detection target. By appropriately dimensioning and/or chemically modifying the scRNAs, only the product of signal transduction, and not the reactants or intermediates, is efficiently processed by Dicer, yielding siRNAs. These mechanism studies explore diverse design principles for engineering scRNA signal transduction cascades including reactant stability vs metastability, catalytic vs noncatalytic transduction, pre- vs post-transcriptional transduction, reactant and product molecularity, and modes of molecular self-assembly and disassembly.

Novel secondary organic aerosol (SOA) products from the monoterpene alpha-pinene with unique dimer-forming properties have been identified as lactone-containing terpenoic acids, i.e., terpenylic and 2-hydroxyterpenylic acid, and diaterpenylic acid acetate. The structural characterizations were based on the synthesis of reference compounds and detailed interpretation of mass spectral data. Terpenylic acid and diaterpenylic acid acetate are early oxidation products generated upon both photooxidation and ozonolysis, while 2-hydroxyterpenylic acid is an abundant SOA tracer in ambient fine aerosol that can be explained by further oxidation of terpenylic acid. Quantum chemical calculations support that noncovalent dimer formation involving double hydrogen bonding interactions between carboxyl groups of the monomers is energetically favorable. The molecular properties allow us to explain initial particle formation in laboratory chamber experiments and are suggested to play a role in new particle formation and growth above forests, a natural phenomenon that has fascinated scientists for more than a century.

The rational design of novel triarylmethyl (trityl)-based mass tags (MT) for mass-spectrometric (MS) applications is described. We propose a "pK(R+) rule" to correlate the stability of trityl carbocations with their MS performance: trityls with higher pK(R+) values ionise and desorb better. Trityl blocks were synthesised that have high pK(R+) values and are stable in conditions of MS analysis; these MTs can be ionised by matrix as well as irradiation with a 337 nm nitrogen laser. (13)C-Labelled tags were prepared for MS quantitation applications. Moreover, the tags were equipped with a variety of functional groups allowing conjugation with different functionalities within (bio)molecules to enhance the MS characteristics of the latter. The MS behaviour of model polycationic trityl compounds with and without the matrix was studied to reveal that poly-trityl clusters are always singly charged under the (MA)LDI-TOF conditions. Several peptide-trityl conjugates were prepared and comparisons revealed a beneficial effect of trityl tags on the conjugate detection in MS. Trityl compounds containing para-methoxy- and dimethylamine groups, as well as a xanthene fragment, showed considerable enhancement in MS detection of model peptides; thus they are promising tools for proteomic applications. Dimethoxytrityl derivatives allow one to distinguish between Arg- and Lys-containing peptides. Maleimido trityl derivatives are suitable for the efficient derivatisation of thiol-containing peptides in pyridine.

Organosulfates of isoprene, alpha-pinene, and beta-pinene have recently been identified in both laboratory-generated and ambient secondary organic aerosol (SOA). In this study, the mechanism and ubiquity of organosulfate formation in biogenic SOA is investigated by a comprehensive series of laboratory photooxidation (i.e., OH-initiated oxidation) and nighttime oxidation (i.e., NO3-initiated oxidation under dark conditions) experiments using nine monoterpenes (alpha-pinene, beta-pinene, d-limonene, l-limonene, alpha-terpinene, gamma-terpinene, terpinolene, Delta(3)-carene, and beta-phellandrene) and three monoterpenes (alpha-pinene, d-limonene, and l-limonene), respectively. Organosulfates were characterized using liquid chromatographic techniques coupled to electrospray ionization combined with both linear ion trap and high-resolution time-of-flight mass spectrometry. Organosulfates are formed only when monoterpenes are oxidized in the presence of acidified sulfate seed aerosol, a result consistent with prior work. Archived laboratory-generated isoprene SOA and ambient filter samples collected from the southeastern U.S. were reexamined for organosulfates. By comparing the tandem mass spectrometric and accurate mass measurements collected for both the laboratory-generated and ambient aerosol, previously uncharacterized ambient organic aerosol components are found to be organosulfates of isoprene, alpha-pinene, beta-pinene, and limonene-like monoterpenes (e.g., myrcene), demonstrating the ubiquity of organosulfate formation in ambient SOA. Several of the organosulfates of isoprene and of the monoterpenes characterized in this study are ambient tracer compounds for the occurrence of biogenic SOA formation under acidic conditions. Furthermore, the nighttime oxidation experiments conducted under highly acidic conditions reveal a viable mechanism for the formation of previously identified nitrooxy organosulfates found in ambient nighttime aerosol samples. We estimate that the organosulfate contribution to the total organic mass fraction of ambient aerosol collected from K-puszta, Hungary, a field site with a similar organosulfate composition as that found in the present study for the southeastern U.S., can be as high as 30%.

Certain carbohydrates (rhamnose, 3-O-methyl rhamnose, and galactosamine) have been demonstrated to be present in Bacillus anthracis spores but absent in vegetative cells. Others have demonstrated that these spore-specific sugars are constituents of the glycoprotein BclA. In the current work, spore extracts were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A second collagen-like glycoprotein, BclB, was identified in B. anthracis. The protein moiety of this glycoprotein was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MS) and the carbohydrate components by gas chromatography-mass spectrometry and tandem mass spectrometry. Spore-specific sugars were also demonstrated to be components of BclB.

We characterized the differential accessibility of the nicotinic acetylcholine receptor alpha1 subunit in the open, closed, and desensitized states by using electrophysiology-coordinated photolabeling by several lipophilic probes followed by mass spectrometric analysis. Voltage-clamped oocytes expressing receptors were preincubated with one of the lipophilic probes and were continually exposed to acetylcholine; UV irradiation was applied during 500-ms pulses to + 40 or to -140 mV (which produced closed or approximately 50% open receptors, respectively). In the open state, there was specific probe incorporation within the N-terminal domain at residues that align with the beta8-beta9 loop of the acetylcholine-binding protein. In the closed state, probe incorporation was identified at several sites of the N-terminal domain within the conserved cysteine loop (residues 128-142), the cytoplasmic loop (M3-M4), and M4. The labeling pattern in the M4 region is consistent with previous results, further defining the lipid-exposed face of this transmembrane alpha-helix. These results show regions within the N-terminal domain that are involved in gating-dependent conformational shifts, confirm that the cysteine loop resides at or near the protein-membrane interface, and show that segments of the M3-M4 loop are near to the lipid bilayer.

In a previous study utilizing benzophenone-based topological probes to study conformationally dependent changes in mouse muscle nicotinic acetylcholine receptor (nAChR) topology, electrospray ionization tandem mass spectrometric (ESI-MS/MS) analysis led to a consistent -2.0 Da mass deviation from expected values. In the present study a synthetic peptide, corresponding to nAChR alpha1 subunit residues 130-139, was photolabeled. MS/MS analysis of this peptide using an ion trap confirmed the previously observed mass deviation, associated only with fragment ions that contain the incorporated benzophenone moiety. Analysis of peak profiles for the photolabeled ions does not indicate the typical 'peak fronting' that produces a mass shift when labile ions are prematurely ejected from the ion trap. Rather, hydrogen/deuterium (H/D) exchange experiments support the hypothesis that a chemical rearrangement involving phenyl migration and ketone formation has formed an unexpected oxidized peptide, with molecular mass 2 Da less than that expected, that is isolated for collision-induced dissociation in the ion trap together with the predicted precursor due to the broad ion isolation window specified., (Copyright 2003 John Wiley & Sons, Ltd.)

Unnatural amino acid mutagenesis requires the in vitro production of aminoacyl tRNAs. Bacteriophage T4 RNA ligase is used to ligate a-amino-protected dCA amino acids to 74mer tRNA. Previously, there has been no facile method for evaluating the efficiency of this reaction prior to using the tRNA in translation. We report a novel use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry in monitoring the formation of aminoacyl 76mer tRNA. This method is more efficient and precise than the traditional technique of gel electrophoresis. These MALDI conditions should also prove useful for analyzing aminoacyl tRNAs produced through aminoacyl tRNA synthetases and other methods.

The apparent mass resolution of oligonucleotides in time-of-flight (TOF) mass spectrometers has been examined. In a reflectron TOF instrument, where the isotopic profile can be completely resolved, the apparent resolution matches the instrument's resolving power. In a linear TOF instrument, unresolved isotopic profiles limit the apparent resolution to much lower values than the actual instrument resolution. By using 12C/14N-enriched oligonucleotides, the apparent resolution can be improved significantly. The isotope enrichment method also enhances the signal-to-noise ratio.

Sample preparation for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) of DNA is critical for obtaining high quality mass spectra. Sample impurity, solvent content, substrate surface and environmental conditions (temperature and humidity) all affect the rate of matrix-analyte co-crystallization. As a result, laser fluence threshold for desorption/ionization varies from spot to spot. When using 3-hydroxypicolinic acid (3-HPA) as the matrix, laser fluence higher than the threshold value reduces mass resolution in time-of-flight (TOF) MS as the excess energy transferred to DNA causes metastable decay. This can be overcome by either searching for 'hot' spots or adjusting the laser fluence. However, both solutions may require a significant amount of operator manipulation and are not ideal for automatic measurements. We have added various sugars for crystallization with the matrix to minimize the transfer of excess laser energy to DNA molecules. Fructose and fucose were found to be the most effective matrix additives. Using these additives, mass resolution for DNA molecules does not show noticeable deterioration as laser energy increases. Improved sample preparation is important for the detection of single nucleotide polymorphisms (SNPs) using primer extension with a single nucleotide. During automatic data acquisition it is difficult to routinely detect heterozygous A/T mutations, which requires resolving a mass difference of 9 Da, unless a sugar is added during crystallization.