http://hdl.handle.net/10256/1551 2025-07-27T12:38:22Z 2025-07-27T12:38:22Z Hernández, Natàlia Sánchez Navarro, Juan Manuel http://hdl.handle.net/10256/27026 2025-07-07T09:36:50Z 2025-07-02T00:00:00Z

Validation of a Method for the Determination of Artificial Sweeteners and Caffeine in Soft Drinks: The Impact of Regression Function Selection on Quantification Limits Considering Trueness and Precision Hernández, Natàlia; Sánchez Navarro, Juan Manuel Background: Method quantification limits are typically determined by measuring variability at blank level only, without accounting for the uncertainties associated with the parameters of the calibration function applied. Methods: A method for the determination of artificial sweeteners and caffeine in soft drinks was validated. The effect of chosen regression function on quantification limits was assessed, considering both trueness and precision. Results: The validated method exhibited heteroscedasticity for all analytes, which is common in experimental methods. A linear response was observed within the working range for sweeteners, while a quadratic regression was required for caffeine. Due to the heteroscedasticity nature of the responses, weighted regressions were necessary to obtain the lowest method quantification limits, allowing for accurate (i.e., unbiased and precise) estimates at the lower end of the calibration range. Under weighted conditions, the regression equations obtained, with an upper range set at 600 mg/L , were as follows: y = 3.9 + 58.9x for acesulfame K; y = 0.8 + 185.1x for saccharin; y = 3.5 + 43.3x for aspartame, and y = −7 + 159x − 0.242x2 for caffeine. The method quantification limits determined using weighted regressions were 2 mg/L for each analyte, whereas these limits increased to 20 mg/L when non-weighted regressions were applied. Conclusions: The choice of regression function for transforming instrumental signals into analyte concentrations significantly affects the determination of quantification limits, owing to the inherent heteroscedasticity of analytical and bioanalytical calibrations. Weighted regressions are essential for producing accurate estimates at lower concentration levels. Applying weighted regression in the context of heteroscedastic calibrations can lead to quantification limits that are more than 10 times lower than unweighted approaches

2025-07-02T00:00:00Z Wieland, Mona Luizaga, Jonnely Duran i Rebenaque, Cristina Germscheid, Barbara Rein, Johanna Bruckmann, Astrid Hiefinger, Caroline Osuna Oliveras, Sílvia Hupfeld, Andrea http://hdl.handle.net/10256/26970 2025-06-25T12:42:57Z 2025-05-06T00:00:00Z

Reversible Substrate-Specific Photocontrol of the Chemotherapeutic Asparaginase(-Glutaminase) from Escherichia coli Wieland, Mona; Luizaga, Jonnely; Duran i Rebenaque, Cristina; Germscheid, Barbara; Rein, Johanna; Bruckmann, Astrid; Hiefinger, Caroline; Osuna Oliveras, Sílvia; Hupfeld, Andrea Photoswitchable unnatural amino acids are valuable engineering tools in biotechnology, particularly for the reversible control of enzymes with light. Here, we explore some basic principles of this protein engineering technique to simplify its approach and increase its success rate. To this end, we have selected Escherichia coli type II asparaginase (EcAII), which is a prominent chemotherapeutic enzyme that is limited by detrimental side effects associated with its promiscuous glutaminase activity. Incorporation of phenylalanine-4′-azobenzene (AzoF) combined with extensive biophysical characterizations identified two light-sensitive variants, in which glutamine hydrolysis could be reversibly (de)activated up to 9-fold, whereas asparaginase hydrolysis was only marginally light-responsive. Computationally determined conformational landscapes elucidated this substrate-specificity of photocontrol defining a clear engineering principle: An exchange between less and more productive states at the active site helps AzoF to reshape the conformational landscape and makes enzymes more susceptible toward photocontrol. Moreover, our findings mark EcAII-AzoF variants as potential chemotherapeutic precursors

2025-05-06T00:00:00Z Huang, Ya-Shan Xu, Hong-Lei Tian, Wen-Juan Li, Zisheng Escayola Gordils, Sílvia Solà i Puig, Miquel Muñoz-Castro, Alvaro Sun, Zhong-Ming http://hdl.handle.net/10256/26905 2025-06-12T11:16:25Z 2025-03-05T00:00:00Z

[Co3@Ge6Sn18]5−: A Giant σ-Aromatic Cluster Analogous to H3+ and Li3+ Huang, Ya-Shan; Xu, Hong-Lei; Tian, Wen-Juan; Li, Zisheng; Escayola Gordils, Sílvia; Solà i Puig, Miquel; Muñoz-Castro, Alvaro; Sun, Zhong-Ming Aromaticity is one of the most important concepts in chemistry and has been successfully extended to all-metal clusters. However, the study of all-metallic aromatic clusters remains in its early stages, with σ-aromatic clusters mostly limited to small sizes (≤12) that often require external stabilization. In this work, we report the first Ge/Sn-based trimer, [Co3@Ge6Sn18]5−, which can be rationalized as the fusion of three [Co@Ge3Sn64−] units via a Ge3 face. Theoretical studies have revealed that two σ-electrons are delocalized across the entire trimer, with the spherical aromaticity of each [Co@Ge3Sn6] unit and the global σ-aromaticity of [Co3@Ge6Sn18]5− further supported by its electron delocalization and magnetic behavior. As a result, this trimer can be viewed as a giant σ-aromatic counterpart to the triatomic H3+ and Li3+. Our findings suggest the potential for synthesizing cluster-of-cluster analogs of discrete all-metallic aromatic species, such as Al42−, and further enhance our understanding of chemical bonding

2025-03-05T00:00:00Z Chen, Pengfei Li, Yafei Ma, Jing Zhu, Jun Xie, Jin Solà i Puig, Miquel Zhu, Congqing Zhu, Qin http://hdl.handle.net/10256/26904 2025-06-12T11:01:39Z 2025-04-18T00:00:00Z

Neutral All-Metal σ-Aromaticity in a Rhombic Cluster Chen, Pengfei; Li, Yafei; Ma, Jing; Zhu, Jun; Xie, Jin; Solà i Puig, Miquel; Zhu, Congqing; Zhu, Qin Aromaticity is a cornerstone concept in chemistry, playing a crucial role in understanding molecular stability and reactivity. Traditionally, aromaticity has been primarily associated with cyclic planar conjugated organic molecules composed solely of carbon, but it has recently expanded to include metal-containing systems. However, metal-only aromatics remain extremely scarce. Here, we present the first neutral all-metal aromatic cluster with a rhombic geometry. X-ray crystallography reveals that the rhombic Al2Pd2 core is stabilized by an innovative double-layer N-P ligand framework, featuring essentially the same Al-Pd bond lengths (2.4706(4) and 2.4636(4) Å) and two planar tetracoordinate Al centers. Quantum chemical calculations provide compelling evidence for the two-electron σ-aromaticity in this molecule. Further research on the reactivity of the σ-aromatic Al2Pd2 cluster reveals it can accept lone-pair electron coordination and act as a two-electron reducing agent. This study not only extends the concept of aromaticity to neutral all-metal rhombic systems but also opens new horizons for the synthesis and exploration of novel all-metal aromatic clusters

2025-04-18T00:00:00Z