Difference In Melting Temperature Research Articles

Influence of extraction variables on the structure and physical properties of salmon gelatin

This work focuses on investigating the effect of extraction conditions (pH and time) on the biochemical and physical properties of salmon gelatin (SG).SG was extracted from salmon skins under different pH and time conditions at 60 °C. The characterization of the material considered proximate composition, amino acid profile, molecular weight (MW), gel strength, X-Ray diffraction, thermal properties, dynamic mechanical properties and dynamic vapour sorption analysis.Results showed that higher protein content was obtained with extraction condition pH5/2h, while lower protein content was obtained at condition pH3/5h. Extraction performed at pH5 produced SG with MW > 120 kDa, while processing condition at pH3 resulted in MW bands distributed between 20 and 100 kDa. Higher contents of proline and hydroxyproline were detected in SG with high MW. This behaviour was directly correlated with gel strength and thermo-mechanical properties: higher gel strength and E’ modulus were observed in SG with high MW, suggesting higher amount of triple helical structures in gelatin matrix. This was also supported by higher values of tanδ detected as the MW of SG decreased. This may be related with decreasing the crystalline fraction of SG. Thermal properties revealed no significant differences in melting temperature and glass transition temperature values among samples. The melting energy was significantly lower for SG with lower MW. This was confirmed by X-Ray diffraction where the intensity of the diffraction peak at ∼2θ = 8° significantly decreased for SG extracted under more aggressive conditions. Finally, gelatin extracted under mild conditions showed higher moisture content, which was in agreement with higher amounts of triple-helix structures.Our results suggest the possibility to modulate the physical properties of SG by tuning the extraction process to obtain tailored gelatin structures for high-value applications in food technology, tissue engineering and biomedicine.

Detecting and Differentiating Phytoplasmas Belonging to Subgroups 16SrIV-A and 16SrIV-D Associated With Lethal Declines of Palms in Florida Using qPCR and High-Resolution Melt Analysis (HRMA).

Lethal yellowing (LY) and Texas Phoenix palm decline (TPPD) are two important phytoplasma diseases of palms in Florida. Both have been responsible for major economic losses historically and remain a constant threat to the sustainability of palm production in the landscaping and nursery industries in Florida. These two diseases cause rapid, lethal decline in afflicted palms, so rapid detection and identification is crucial to implement appropriate management strategies to reduce further spread and losses. In this study, a qPCR assay was developed to detect and identify the causal agents of LY and TPPD. Based on sequence data of the 16S gene for the 16SrIV-A phytoplasma (LY) and the 16SrIV-D phytoplasma (TPPD), two regions were identified in the gene that possessed sufficient variation to yield amplicons with measurable differences in melting temperature based on high resolution melt analysis (HRMA). One region was in the 5' region and the other was located in the 3' region of the gene. Products from both regions yielded amplicons with significantly different melting temperatures between the two phytoplasma strains. This research allows for the detection and identification of phytoplasmas in palms rapidly by eliminating many lengthy and post-PCR steps commonly used in phytoplasma identification.

Discrimination of three genetically close Aspergillus species by using high resolution melting analysis applied to indoor air as case study

BackgroundIndoor air pollution caused by fungal contamination is suspected to have a public health impact. Monitoring of the composition of the indoor airborne fungal contaminants is therefore important. To avoid problems linked to culture-dependent protocols, molecular methods are increasingly being proposed as an alternative. Among these molecular methods, the polymerase chain reaction (PCR) and the real-time PCR are the most frequently used tools for indoor fungal detection. However, even if these tools have demonstrated their appropriate performance, some of them are not able to discriminate between species which are genetically close. A solution to this could be the use of a post-qPCR high resolution melting (HRM) analysis, which would allow the discrimination of these species based on the highly accurate determination of the difference in melting temperature of the obtained amplicon. In this study, we provide a proof-of-concept for this approach, using a dye adapted version of our previously developed qPCR SYBR®Green method to detect Aspergillus versicolor in indoor air, an important airborne fungus in terms of occurrence and cause of health problems. Despite the good performance observed for that qPCR method, no discrimination could previously be made between A. versicolor, Aspergillus creber and Aspergillus sydowii.MethodsIn this study, we developed and evaluated an HRM assay for the discrimination between A. versicolor, Aspergillus creber and Aspergillus sydowii.ResultsUsing HRM analysis, the discrimination of the 3 Aspergillus species could be made. No false positive, nor false negatives were observed during the performance assessment including 20 strains of Aspergillus. The limit of detection was determined for each species i.e., 0.5 pg of gDNA for A. creber and A. sydowii, and 0.1 pg of gDNA for A. versicolor. The HRM analysis was also successfully tested on environmental samples.ConclusionWe reported the development of HRM tools for the discrimination of A. versicolor, A. creber and A. sydowii. However, this study could be considered as a study case demonstrating that HRM based on existing qPCR assays, allows a more accurate identification of indoor air contaminants. This contributes to an improved insight in the diversity of indoor airborne fungi and hence, eventually in the causal link with health problems.

Effect of the flyer material on the interface phenomena in aluminium and copper explosive welds

The effect of physical and mechanical properties of three different flyers on the interface phenomena of partially overlapped explosive welds, using the same base plate material, was studied. Flyers of Copper Cu-DHP and aluminium alloy 6082 (tempers T6 and O) were welded to AA6082-T6 base plates. The morphology of the weld interface is strongly influenced by the physical and mechanical properties of the flyer. In the interface of the aluminium welds, the use of a flyer of lower hardness and yield strength than the base plate results in asymmetrical waves, with bigger amplitude and smaller wavelength than the weld series of similar temper, and higher mechanical properties. The copper-aluminium welds presented flat interfaces, mainly because of the significant differences in melting temperature and density between the copper flyer and the aluminium base plate. Considering these results and analysing several dissimilar welds carried out by other authors it was found that when the product of density and melting temperature ratios between the flyer and the base plate exceeds a certain value, there is no formation of waves at the interface of the metals. Furthermore, for the Cu-Al welds, the CuAl2 (θ) intermetallic phase was formed on the bond zone.

Effect of Weld Parameters on Mechanical Properties of Friction Stir Welded Aluminium Alloy6082-T6 and Soft Steel (Mild Steel)

Friction Stir Welding is a solid state joining process where a tool with pin, which is non-consumable, is used to join the two facing workpieces without melting them. This technique was invented in 1991 by The Welding Institute, United Kingdom.  Joining of Non-Ferrous and Ferrous materials like Aluminium to Steel finds its application in various industrial applications. Due to the large differences in melting temperature, physical and chemical properties makes it difficult to control weld and defects during welding. Formations of intermetallic compounds at the interface due to very low solubility of Fe in Al are detrimental to joint efficiency. The butt joint between Al 6082-T6 and Steel is formed by friction stir welding is carried out on a friction stir welder. Tensile tests and hardness test are conducted on the weld specimens to assess the change in mechanical and metallurgical behaviour. The fractured tensile specimens are subjected to fractography analysis in order to find out the origin of cracks and the fracture mechanism involved.

Crystallization and Gelation Behavior of Low- and High Melting Waxes in Rice Bran Oil: a Case-Study on Berry Wax and Sunflower Wax

Low-melting berry wax (BEW) has proven to be a good oil gelator with a positive contribution to the consistency and flexibility of the structured oil. Nevertheless, the properties of BEW and the corresponding oleogel have not yet been investigated in-depth. In this research, the difference in crystallization and gelling behavior between sunflower wax (SW), a high melting wax, and BEW, a low-melting wax, in rice bran oil (RBO) was investigated. The difference in melting and crystallization temperatures can be explained by the different chemical composition (long-chain wax esters in SW and short-chain fatty acids in BEW). The heterogeneity in crystal habits (unidirectional platelets versus microcrystalline particles) and polymorphism (orthorhombic versus hexagonal) are responsible for the varying gel strength and hardness of the respective SW- and BEW-oleogels. The microcrystalline BEW particles aligned and reorganized during 1-month storage at 5 °C, which leaded to an increase in the gel strength and hardness of BEW-oleogel. The gelling property of SW-oleogel however did not significantly differ after 4 weeks at 5 °C, despite of the appearance of spherulitic crystalline clusters. The changes in the physical properties of wax-based oleogels during storage time were further explored using differential scanning calorimetry, polarized light microscope, powder X-ray diffraction and rheology.

Effect of annealing on the properties of polylactide/poly(butylene carbonate) blend

AbstractThe microstructure evolution of partial miscible polylactide/poly(butylene carbonate) (PLA/PBC) blend during annealing, including the variation in crystalline structure of PLA and PBC, the morphologies of PBC particles, and the relaxation of chain segments in the amorphous region of PLA, is investigated in detail. Based on the significant difference in melting temperature, phase separation arises as a result of the occurrence of crystallization of PLA and is further enhanced due to the crystallization of PBC. The glass transition temperature Tg of the PLA phase in the phase separation blend is significantly higher than that of the pure PLA due to increasing crystallinity. The increasing annealing time resulted in enhanced phase separation, as reflected in the harsher morphology, the decrease of molecular dynamics, and the reduction amount of the amorphous domain. It can be verified by the interaction parameter C values at various annealing conditions from the yield stress data. Therefore, blend is aptitude to elongation decrease and the toughening micromechanism changes, while the plastic deformation is the important energy dissipation process for quenched PLA/PBC blend. Debonding of the PBC particles followed by plastic void growth of the PLA matrix is the major toughening micro‐mechanisms for phase separation blend.

Supercritical CO2 Extraction as an Effective Pretreatment Step for Wax Extraction in a Miscanthus Biorefinery

The use of supercritical carbon dioxide (scCO2) to extract valuable lipophilic compounds from miscanthus was investigated and subsequent enzymatic saccharification was carried out to determine the impact of scCO2 extraction on downstream processing of miscanthus. Two miscanthus genotypes (Miscanthus x. giganteus and Miscanthus sinensis) were investigated and characterized. A diverse range of molecules were detected including long-chain hydrocarbons, fatty acids, n-policosanols, aldehydes, wax esters, sterols and steroid ketones. Quantification data indicates that there is a considerable difference among each species in the quantities of specific compounds. The waxes also exhibited significant differences in melting temperature, thus illustrating the opportunity for utilization in various applications. In addition to the isolation of valuable chemical compounds, the scCO2 pretreatment also had a beneficial effect on the downstream processing of the biomass. The total sugars released after saccharification ...

Use of the melting curve assay as a means for high-throughput quantification of Illumina sequencing libraries.

Background. Multiplexed sequencing is commonly performed on massively parallel short-read sequencing platforms such as Illumina, and the efficiency of library normalisation can affect the quality of the output dataset. Although several library normalisation approaches have been established, none are ideal for highly multiplexed sequencing due to issues of cost and/or processing time.Methods. An inexpensive and high-throughput library quantification method has been developed, based on an adaptation of the melting curve assay. Sequencing libraries were subjected to the assay using the Bio-Rad Laboratories CFX ConnectTM Real-Time PCR Detection System. The library quantity was calculated through summation of reduction of relative fluorescence units between 86 and 95 °C.Results.PCR-enriched sequencing libraries are suitable for this quantification without pre-purification of DNA. Short DNA molecules, which ideally should be eliminated from the library for subsequent processing, were differentiated from the target DNA in a mixture on the basis of differences in melting temperature. Quantification results for long sequences targeted using the melting curve assay were correlated with those from existing methods (R2 > 0.77), and that observed from MiSeq sequencing (R2 = 0.82).Discussion.The results of multiplexed sequencing suggested that the normalisation performance of the described method is equivalent to that of another recently reported high-throughput bead-based method, BeNUS. However, costs for the melting curve assay are considerably lower and processing times shorter than those of other existing methods, suggesting greater suitability for highly multiplexed sequencing applications.

Combination probes with intercalating anchors and proximal fluorophores for DNA and RNA detection.

A new class of modified oligonucleotides (combination probes) has been designed and synthesised for use in genetic analysis and RNA detection. Their chemical structure combines an intercalating anchor with a reporter fluorophore on the same thymine nucleobase. The intercalator (thiazole orange or benzothiazole orange) provides an anchor, which upon hybridisation of the probe to its target becomes fluorescent and simultaneously stabilizes the duplex. The anchor is able to communicate via FRET to a proximal reporter dye (e.g. ROX, HEX, ATTO647N, FAM) whose fluorescence signal can be monitored on a range of analytical devices. Direct excitation of the reporter dye provides an alternative signalling mechanism. In both signalling modes, fluorescence in the unhybridised probe is switched off by collisional quenching between adjacent intercalator and reporter dyes. Single nucleotide polymorphisms in DNA and RNA targets are identified by differences in the duplex melting temperature, and the use of short hybridization probes, made possible by the stabilisation provided by the intercalator, enhances mismatch discrimination. Unlike other fluorogenic probe systems, placing the fluorophore and quencher on the same nucleobase facilitates the design of short probes containing multiple modifications. The ability to detect both DNA and RNA sequences suggests applications in cellular imaging and diagnostics.

Formation of a Segregated Electrically Conductive Network Structure in a Low-Melt-Viscosity Polymer for Highly Efficient Electromagnetic Interference Shielding

A segregated electrically conductive network structure has been well demonstrated to efficiently improve electrical and electromagnetic interference (EMI) shielding performance owing to the controllable assembling of conductive additives in polymer matrices; however, up to now, the polymer matrices are mainly limited to high-melt-viscosity polymers (e.g., ultrahigh molecular weight or cross-linked polymers). In the current work, we proposed a strategy to form a typical segregated structure in a low-melt-viscosity polymer, i.e., poly(lactic acid) (PLA), making use of the melting temperature difference of crystallites. Poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) were first melt mixed, then crystallized, herein the resultant blend consisted of homocrystallites (hc) and stereocomplex crystallites (sc), and, interestingly, spontaneously granulated into 100 μm particles during melt mixing and crystallizing. The mixture of PLA crystallite granules and carbon nanotubes (CNTs) was compression molded at a tem...

Microstructural Characterization of Friction Stir Welded Aluminum-Steel Joints

This work focuses on the microstructural characterization of aluminum to steel friction stir welded joints. Lap weld configuration coupled with scribe technology used for the weld tool have produced joints of adequate quality, despite the significant differences in hardness and melting temperatures of the alloys. Common to friction stir processes, especially those of dissimilar alloys, are microstructural gradients including grain size, crystallographic texture, and precipitation of intermetallic compounds. Because of the significant influence that intermetallic compound formation has on mechanical and ballistic behavior, the characterization of the specific intermetallic phases and the degree to which they are formed in the weld microstructure is critical to predicting weld performance. This study used electron backscatter diffraction, energy dispersive spectroscopy, scanning electron microscopy, and Vickers micro-hardness indentation to explore and characterize the microstructures of lap friction stir welds between an applique 6061-T6 aluminum armor plate alloy and a RHA homogeneous armor plate steel alloy. Macroscopic defects such as micro-cracks were observed in the cross-sectional samples, and binary intermetallic compound layers were found to exist at the aluminum-steel interfaces of the steel particles stirred into the aluminum weld matrix and across the interfaces of the weld joints. Energy dispersive spectroscopy chemical analysis identified the intermetallic layer as monoclinic Al3Fe. Dramatic decreases in grain size in the thermo-mechanically affected zones and weld zones that evidenced grain refinement through plastic deformation and recrystallization. Crystallographic grain orientation and texture were examined using electron backscatter diffraction. Striated regions in the orientations of the aluminum alloy were determined to be the result of the severe deformation induced by the complex weld tool geometry. Many of the textures observed in the weld zone and thermo-mechanically affected zones exhibited shear texture components; however, there were many textures that deviated from ideal simple shear. Factors affecting the microstructure which are characteristic of the friction stir welding process, such as post-recrystallization deformation and complex deformation induced by tool geometry were discussed as causes for deviation from simple shear textures.

Visual System Homeobox 1 (VSX1) Gene Analysis in Keratoconus: Design of Specific Primers and DNA Amplification Protocols for Accurate Molecular Characterization.

Keratoconus is an ocular degeneration characterized by the thinning of corneal stroma that may lead to varying degrees of myopia and visual impairment. Genetic factors have been reported in the pathology of keratoconus where Asians have a higher incidence, earlier onset, and undergo earlier corneal grafts compared to Caucasians. The visual system homeobox 1 (VSX1) gene forms part of a paired-like homeodomain transcription factor which is responsible for ocular development. The gene was marked as a candidate in genetic studies of keratoconus in various populations. Single nucleotide polymorphisms (SNPs) in the VSX1 gene have been reported to be associated with keratoconus. The detection of the SNPs involves DNA amplification of the VSX1 gene followed by genomic sequencing. Thus, the objective of this study aims to establish sensitive and accurate screening protocols for the molecular characterization of VSX1 polymorphisms. Keratoconic (n = 74) and control subjects (n = 96) were recruited based on clinical diagnostic tests and selection criteria. DNA extracted from the blood samples was used to genotype VSX1 polymorphisms. In-house designed primers and optimization of PCR conditions were carried out to amplify exons 1 and 3 of the VSX1 gene. PCR conditions including percentage GC content, melting temperatures, and differences in melting temperatures of primers were evaluated to produce sensitive and specific DNA amplifications. Genotyping was successfully carried out in 4 exons of the VSX1 gene. Primer annealing temperatures were observed to be crucial in enhancing PCR sensitivity and specificity. Annealing temperatures were carefully evaluated to produce increased specificity, yet not allowing sensitivity to be compromised. In addition, exon 1 of the VSX1 gene was amplified using 2 different sets of primers to produce 2 smaller amplified products with absence of non-specific bands. DNA amplification of exons 1 and 3 consistently showed single band products which were successfully sequenced to yield reproducible data. The use of in-house designed primers and optimized PCR conditions allowed sensitive and specific DNA amplifications that produced distinct single bands. The in-house designed primers and DNA amplification protocols established in this study provide an addition to the current repertoire of primers for accurate molecular characterization of VSX1 gene polymorphisms in keratoconus research.

Development of genome-wide InDel markers and their integration with SSR, DArT and SNP markers in single barley map.

BackgroundDevelopment of molecular markers such as SSR (simple sequence repeat), DArT (diversity arrays technology) and SNP (single nucleotide polymorphism) is fundamental for linkage map construction and QTL mapping. However, DArT and SNP genotyping require special tools, and detection of SSR polymorphisms requires time-consuming polyacrylamide electrophoresis. Furthermore, many markers have been mapped in different populations such that their genetic positions are inconsistent. Recently, InDel (insertion and deletion) markers have become popular in genetic map construction and map-based cloning.ResultsAligning genomic DNA sequences in two barley cultivars (Morex and Barke) identified 436,640 InDels. We designed 1140 InDel markers across the barley genome with an average genetic distance of 1 cM, each having a unique location in the barley genome. High-resolution melting (HRM) technology was used to genotype 55 InDel markers; those PCR amplicons with melting temperature differences >0.3 °C were ideal for HRM genotyping. The 1140 InDel markers together with 383 SSRs, 3909 gene-based SNPs and 1544 DArT markers were integrated into single barley genetic map according to their physical map positions.ConclusionsHigh-density InDel markers with specific genome locations were developed, with 6976 molecular markers (SSRs, DArTs, SNPs and InDels) integrated into single barley genetic map. HRM genotyping of the InDel markers each with single PCR band will facilitate quick map construction and gene fine-mapping.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2027-x) contains supplementary material, which is available to authorized users.

In Search of an Efficient Photoswitch for Functional RNA: Design Principles from a Microscopic Analysis of Azobenzene-linker-RNA Dynamics with Different Linkers.

The design of optimal photoswitches to regulate nucleic acid functionality is a considerable challenge. Azobenzene switches that are covalently bound to the nucleic acid backbone are a paradigm example that has been studied using different types of linker species connecting the chromophore to the backbone. To support experimental efforts to construct optimal azobenzene-linker-RNA combinations, we introduce here a systematic approach for theoretical analysis, which provides criteria for the local embedding of the chromophore via a chosen linker. Using a local reference frame adapted to the chromophore, quantitative measures are provided for (i) the propensity of stacking in competition with a drift toward the minor or major groove, (ii) the tendency to disrupt the native hydrogen bond network, (iii) the structural flexibility of the chromophore-linker combination, and (iv) the correlations with the presence of a base in the opposite strand. Large differences in structural stability between the trans and cis forms of the azobenzene chromophore, according to these criteria, indicate good functionality and lead to significant differences in melting temperatures. In particular, a recently synthesized deoxyribose linker proves optimal within the set of azobenzene-linker-RNA combinations considered.

Mechanical alloying and thermal analysis of Ta–Ti alloys

Tantalum–titanium alloys have widespread potential in biomedical applications due to their superior biocompatibility, favorable mechanical properties, high corrosion resistance, and ability to exhibit shape memory behavior. However, this system is plagued by processing difficulties due to significant differences in melting temperatures, specific weights, and vapor pressures of Ta and Ti. In the present study, mechanical alloying (MA) using high‐energy ball milling of Ti–xTa (where x = 50, 60, 70, and 85 wt%) was investigated. The alloyed powders were characterized by X-ray diffraction, electron microscopy (SEM and TEM), and differential scanning calorimetry. It was established that α-Ti (hcp) gradually dissolves into α-Ta (bcc), with the alloyed particles becoming chemically homogeneous as a bcc structure. This structure corresponds to a meta-stable phase and should decompose to yield two solid solutions, Ti-rich hcp and Ta-rich bcc. To overcome this thermodynamic preference, MA-generated Ta–Ti bcc solid solution powders possess relatively high internal strain energy.

SsDNA Pairing Accuracy Increases When Abasic Sites Divide Nucleotides into Small Groups.

Accurate sequence dependent pairing of single-stranded DNA (ssDNA) molecules plays an important role in gene chips, DNA origami, and polymerase chain reactions. In many assays accurate pairing depends on mismatched sequences melting at lower temperatures than matched sequences; however, for sequences longer than ~10 nucleotides, single mismatches and correct matches have melting temperature differences of less than 3°C. We demonstrate that appropriately grouping of 35 bases in ssDNA using abasic sites increases the difference between the melting temperature of correct bases and the melting temperature of mismatched base pairings. Importantly, in the presence of appropriately spaced abasic sites mismatches near one end of a long dsDNA destabilize the annealing at the other end much more effectively than in systems without the abasic sites, suggesting that the dsDNA melts more uniformly in the presence of appropriately spaced abasic sites. In sum, the presence of appropriately spaced abasic sites allows temperature to more accurately discriminate correct base pairings from incorrect ones.

Rapid identification of Helicoverpa armigera and Helicoverpa zea (Lepidoptera: Noctuidae) using ribosomal RNA internal transcribed spacer 1.

Rapid identification of invasive species is crucial for deploying management strategies to prevent establishment. Recent Helicoverpa armigera (Hübner) invasions and subsequent establishment in South America has increased the risk of this species invading North America. Morphological similarities make differentiation of H. armigera from the native Helicoverpa zea (Boddie) difficult. Characteristics of adult male genitalia and nucleotide sequence differences in mitochondrial DNA are two of the currently available methods to differentiate these two species. However, current methods are likely too slow to be employed as rapid detection methods. In this study, conserved differences in the internal transcribed spacer 1 (ITS1) of the ribosomal RNA genes were used to develop species-specific oligonucleotide primers that amplified ITS1 fragments of 147 and 334 bp from H. armigera and H. zea, respectively. An amplicon (83 bp) from a conserved region of 18S ribosomal RNA subunit served as a positive control. Melting temperature differences in ITS1 amplicons yielded species-specific dissociation curves that could be used in high resolution melt analysis to differentiate the two Helicoverpa species. In addition, a rapid and inexpensive procedure for obtaining amplifiable genomic DNA from a small amount of tissue was identified. Under optimal conditions, the process was able to detect DNA from one H. armigera leg in a pool of 25 legs. The high resolution melt analysis combined with rapid DNA extraction could be used as an inexpensive method to genetically differentiate large numbers of H. armigera and H. zea using readily available reagents.

Smooth change, mechanistic fluctuation: thermodynamic system drift in protein evolution.

Smooth change, mechanistic fluctuation: thermodynamic system drift in protein evolution.

Petrogenesis of Triassic granites from the Nanling Range in South China: Implications for geochemical diversity in granites

Abstract A combined study of whole-rock major-trace elements and Sr–Nd isotopes, zircon U–Pb ages, Hf and O isotopes as well as biotite geochemistry was carried out for Triassic granite intrusions from the Nanling Range in South China. The results provide insights into the effects of source composition and melting conditions on the geochemical diversity of granites. The granites of interest are peraluminous, and contain primary muscovite and tourmaline. They are characterized by high zircon δ18O values of > 9.0‰, high initial 87Sr/86Sr values of ~ 0.7200, and homogeneous eNd(t) values of − 11.3 to − 9.8, as well as variable zircon eHf(t) values of − 12.2 to − 5.8. Biotite geochemistry is similar to that of common peraluminous granites. An integrated interpretation of these petrological, mineralogical and geochemical data indicates that these granites were derived from partial melting of metasedimentary rocks under variable physicochemical conditions. The differences in whole-rock and biotite geochemistry between the intrusions are ascribed to the variable effects of source heterogeneity and melting temperature. The Luxi intrusion exhibits higher contents of MgO, FeOT, TiO2 and CaO than common melts derived from metasedimentary rocks, tight variations in major-trace elements and homogeneous Sr–Nd isotopic compositions, and homogeneous biotite composition with high Mg# [= Mg / (Mg + Fe) in molar] and lower whole-rock A/CNK values [= Al2O3 / (CaO + Na2O + K2O) in molar]. These can be explained by originating from a relatively mafic metasedimentary source. On the other hand, the geochemical diversity of granites can be caused by the difference in melting temperature in addition to the source heterogeneity. This is suggested by the Xiazhuang and Fucheng intrusions which exhibit similar range of SiO2. Nevertheless, the Fucheng intrusion is ferroan, and high in TiO2, (Na2O + K2O)/CaO, TiO2/MgO, Ga/Al and Zr + Nb + Ce + Y, but low in CaO, MgO and Mg#. Most of its major elements and their ratios are similar to those of A-type granites that were generated from F-rich rocks at high temperatures, consistent with the enrichment of Fe and F in its biotite. Thus, partial melting of a metasedimentary restite at reduced conditions after previous melt extraction is suggested to produce the geochemical feature of A-type granites in the Fucheng intrusion. In contrast, partial melting of fertile metasedimentary rocks would produce normal S-type granites like the Xiazhuang intrusion, with its geochemical variations ascrible to source heterogeneity and differential melting. Therefore, the geochemical composition of granites is primarily dictated by the composition of source rocks in addition to the physicochemical conditions of partial melting.